When You Fetch a Query Do You Have to Msyqli Query Again

Introduction

Before I start, if you lot'd like to run across an fifty-fifty easier way to use MySQLi prepared statements, check out my wrapper class. Also, here's a bully resources to acquire PDO prepared statements, which is the better choice for beginners and about people in full general.

A hack attempt has recently been discovered, and it appears they are trying to accept down the entire database. An impromptu staff meeting has been called at 2am, and everyone in the company is freaking out. Ironically, as the database manager, you remain the calmest. Why? You know that these scrubs are are no lucifer for those prepared statements you coded! In fact, you observe this humorous, as these hackers will likely be annoyed that they wasted their time with futile attempts.

Hopefully this scenario will never happen to your website. Nonetheless, information technology is undoubtedly a good idea to accept proper precautions. If implemented correctly, prepared statements (aka parameterized queries) offer superior protection against SQL injection. You basically just create the query template with placeholder values, and so supervene upon the dummy inputs with the real ones. Escaping is not necessary, since information technology volition care for the values every bit literals; all attempts to inject sql queries will exist interpreted every bit such.

Prepared statements may seem intimidating at kickoff, but one time you get hang of it, it'll seem like second nature to you. The goal of this tutorial is to transform someone with piffling to no cognition of prepared statements, into an proficient.

Disclaimer: Don't actually be as laid dorsum as this database manager. When it comes to security, you lot should never be complacent, no affair how secure y'all think your system is.

How SQL Injection Works

The following iconic comic, known as Bobby Tables, is an excellent portrayal of how an SQL injection set on might work. All credit for the image goes to this site for this classic piece of rhetoric.

Now that we're done with the theory, permit's go to practice. Before I start, if you're wondering exactly how the "Bobby Tables Assail" works, cheque out this explanation.

In a normal MySQL call, you would do something like:

          $proper name = $_POST['name']; $mysqli->query("SELECT * FROM myTable WHERE proper noun='$name'");                  

The problem with this, is that if it is based off of user input, like in the case, and so a malicious user could practise ' OR '1'='1. Now this statement volition always evaluate to truthful, since 1=one. In this case, the malicious user now has access to your entire table. Just imagine what could happen if information technology were a DELETE query instead. Take a look at what is actually happening to the statement.

          SELECT * FROM myTable WHERE name=''            OR 'one'='1'                  

A hacker could do a lot of damage to your site if your queries are set upwardly like this. An easy fix to this would be to practise:

          $name = $mysqli->real_escape_string($_POST['proper noun']); $mysqli->query("SELECT * FROM myTable WHERE name='$name'");                  

Discover how similar to the outset example, I however added quotes to the column value. Without quotes, strings are still equally susceptible to SQL injection. If you'll be using a LIKE clause, then you should as well do addcslashes($escaped, '%_'), since mysqli::real_escape_string won't do this as stated here.

This covers strings, as the function name implies, but what near numbers? You could do (int)$mysqli->real_escape_string($_POST['proper name']), which would certainly work, merely that'south redundant. If you lot're casting the variable to an int, you don't need to escape anything. You are already telling it to substantially make sure that the value will exist an integer. Doing (int)$_POST['proper name'] would suffice. Since it is an integer yous also obviously practice non need to add quotes to the sql column name.

In reality, if you lot follow these instructions perfectly, it should be enough to use mysqli::real_escape_string for strings and (int)$var for integers. Just don't forget to ready the default character set. This tin can be set up in either the php.ini (should exist the default value) like default_charset = "utf-8" and by using $mysqli->set_charset('utf8mb4') on each page that uses $mysqli->real_escape_string(). But only for things that are legal in prepared statements, which are values in a WHERE statement or column values; don't use this for table/cavalcade names or SQL keywords.

Regardless, I still strongly propose using prepared statements, as they are clearly more suited to protect against SQL injection and less decumbent to mistakes, since you don't have to worry nearly manually formatting — instead you merely have to replace dummy placeholders with your values. Of form you'll nonetheless want to filter and sanitize your inputs to prevent XSS however. With prepared statements statements, there are fewer aspects to consider, along with some edge cases to interruption $mysqli->real_escape_string() (Non properly setting the charset is one of the causes.). In summation, there's absolutely no good reason to exist using real_escape_string() over prepared statements. I merely showed how to manually format your queries with it, to show that it's possible. In reality, information technology would be foolish to not use prepared statements to preclude SQL injection.

How MySQLi Prepared Statements Work

In plainly English, this is how MySQLi prepared statements piece of work in PHP:

1. Set up an SQL query with empty values equally placeholders (with a question mark for each value).
2. Bind variables to the placeholders past stating each variable, along with its type.
3. Execute query.

The four variable types allowed:

• i - Integer
• d - Double
• s - String
• b - Blob

A prepared statement, as its name implies, is a way of preparing the MySQL call, without storing the variables. You tell it that variables will go in that location somewhen — just not yet. The best way to demonstrate it is by example.

          $stmt = $mysqli->ready("SELECT * FROM myTable WHERE name = ? AND age = ?"); $stmt->bind_param("si", $_POST['name'], $_POST['age']); $stmt->execute(); //fetching result would go hither, merely volition be covered later $stmt->close();                  

If you've never seen prepared statements earlier, this may await a little weird. Basically what'south happening is that you are creating a template for what the SQL statement will be. In this case, we are selecting everything from myTable, where proper name and age equal ?. The question marking is merely a placeholder for where the values will go.

The bind_param() method is where you attach variables to the dummy values in the prepared template. Detect how in that location are two messages in quotes before the variables. This tells the database the variable types. The s specifies that proper noun will be a string value, while the i forces historic period to be an integer. This is precisely why I didn't add quotation marks around the question marking for name, like I normally would for a string in an SQL call. Yous probably thought I just forgot to, but the reality is that there is simply no need to (In fact, information technology actually won't work if you practise put quotes around the ?, since it will be treated equally a string literal, rather than a dummy placeholder.). You are already telling it that it will exist a string literal when you telephone call bind_param(), so even if a malicious user tries to insert SQL into your user inputs, information technology will nevertheless be treated as a string. $stmt->execute() then actually runs the code; the last line simply closes the prepared statement. We will cover fetching results in the Select department.

Creating a New MySQLi Connection

Creating a new MySQLi is pretty simple. I suggest naming a file chosen mysqli_connect.php and place this file exterior of your root directly (html, public_html) so your credentials are secure. Nosotros'll also exist using exception handling, by utilizing mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT). This might await weird to yous, especially if you've never used a bitwise operator before. Merely all it'southward doing is reporting all errors, while converting them to exceptions, using the mysqli_sql_exception course.

          $mysqli = new mysqli("localhost", "username", "password", "databaseName"); if($mysqli->connect_error) {   leave('Error connecting to database'); //Should be a message a typical user could sympathize in production } mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); $mysqli->set_charset("utf8mb4");                  

A lot of tutorials, including the PHP manual, show how to use $mysqli->connect_error() by printing it in go out() or dice(). But this isn't really necessary (not to mention incredibly stupid, as you will exist printing out this info to the world), since the fault message volition be appended to your fault log anway. The bulletin in exit() should be something a normal user could understand, like exit('Something weird happened').

You would call back that setting the charset to utf-8 in your php.ini would suffice, forth with utf8mb4 for your entire database, but sometimes weird errors happen if you don't set it in your php file likewise, every bit noted here.

You can alternatively instantiate it in a try/take hold of block if you enable internal reporting, which I mention in the error handling section. Delight don't ever report errors straight on your site in production. You'll exist kick yourself for such a silly mistake, since it will impress out your sensitive database information (username, password and database name). Hither'south what your php.ini file should wait like in production: practise both display_errors = Off and log_errors = On . Also, do not echo the error in production.

          mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); try {   $mysqli = new mysqli("localhost", "username", "password", "databaseName");   $mysqli->set_charset("utf8mb4"); } catch(Exception $e) {   error_log($e->getMessage());   go out('Fault connecting to database'); //Should exist a bulletin a typical user could sympathize }                  

If you lot adopt using set_exception_handler() instead of try/take hold of, you tin can do the following to avoid nesting. If you are using this method, you need to sympathize that it will affect every page its in included in. Therefore, you must either reuse the role again with a custom bulletin for each page or use restore_exception_handler() to revert back to the congenital in PHP one. If you fabricated multiple ones, it will go to the previous one your fabricated.

          mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); set_exception_handler(office($e) {   error_log($e->getMessage());   exit('Mistake connecting to database'); //Should be a message a typical user could understand }); $mysqli = new mysqli("localhost", "username", "countersign", "databaseName"); $mysqli->set_charset("utf8mb4");                  

In that location's a very of serious repercussion of using mysqli_report(), which is that it will study your sensitive database information. Y'all have three options to withal apply it just not report your password.

1. You tin can also utilise mysqli_report() strictly on everything except for creating the connectedness if you do information technology the first method I showed with $mysqli->connect_error (countersign non shown) and just place mysqli_report() afterward new mysqli().
2. If you call mysqli_report() earlier creating a connection, then you demand to ensure that it's in a attempt/take hold of block and you lot specifically impress in your error log $e->getMessage(), not $e, which still contains your sensitive information. This evidently strictly applies to the constructor.
3. Employ set_exception_handler() in the same manner as 2 and use $e->getMessage().

I strongly recommend doing one of these methods. Even if y'all are diligent and ensure all your errors but goes in your error log, I personally don't see why anyone would need to log their password. You lot'll already know what the event is anyhow.

Insert, Update and Delete

Inserting, updating and deleting have an identical syntax, and then they will be combined.

Insert

          $stmt = $mysqli->prepare("INSERT INTO myTable (name, age) VALUES (?, ?)"); $stmt->bind_param("si", $_POST['name'], $_POST['age']); $stmt->execute(); $stmt->close();                  

Update

          $stmt = $mysqli->set up("UPDATE myTable Prepare proper name = ? WHERE id = ?"); $stmt->bind_param("si", $_POST['name'], $_SESSION['id']); $stmt->execute(); $stmt->close();                  

Delete

          $stmt = $mysqli->ready("DELETE FROM myTable WHERE id = ?"); $stmt->bind_param("i", $_SESSION['id']); $stmt->execute(); $stmt->close();                  

Get Number of Affected Rows

You may also desire to check the condition of a row you inserted, updated or deleted. Here's how you would it if yous're updating a row.

          $stmt = $mysqli->prepare("UPDATE myTable SET name = ?"); $stmt->bind_param("si", $_POST['proper name'], $_POST['age']); $stmt->execute(); if($stmt->affected_rows === 0) leave('No rows updated'); $stmt->close();                  

In this example, nosotros checked to see if whatever rows got updated. For reference, here'due south the usage for mysqli::$affected_rows render values.

-i - query returned an mistake; redundant if there is already error handling for execute()

0 - no records updated on UPDATE, no rows matched the WHERE clause or no query has been executed

Greater than 0 - returns number of rows afflicted; comparable to mysqli_result::$num_rows for SELECT

Get Rows Matched

A common problem with $mysqli->affectedRows is that it makes it incommunicable to know why information technology returned aught on an UPDATE. This is due to the fact that it prints the amount of rows inverse, and then it makes ambiguous if you update your value(south) with the same data.

An awesome feature that is unique to MySQLi, and doesn't exist in PDO, is the ability to go more info nigh a query. Yous tin can technically reach it in PDO, simply it can only exist washed in the connection, therefore you can't choose.

          $stmt = $mysqli->prepare("UPDATE myTable SET name = ?"); $stmt->bind_param("si", $_POST['proper noun'], $_POST['age']); $stmt->execute(); $stmt->close(); echo $mysqli->info;                  

This will print:

          Rows matched: 1 Changed: 0 Warnings: 0                  

I detect this to be a rather imprudent implementation, as information technology's extremely inelegant to use it as is. Luckily nosotros can change that, by converting it to an associative array. All credit goes practice this helpful commenter on the PHP docs. While using mysqli->info for UPDATE is past far its most mutual use instance, information technology can be used for some other query types also.

          preg_match_all('/(\Due south[^:]+): (\d+)/', $mysqli->info, $matches);  $infoArr = array_combine ($matches[1], $matches[ii]); var_export($infoArr);                  

At present this will output an array.

          ['Rows matched' => '1', 'Changed' => '0', 'Warnings' => '0']                  

Get Latest Master Primal Inserted

          $stmt = $mysqli->gear up("INSERT INTO myTable (proper noun, age) VALUES (?, ?)"); $stmt->bind_param("si", $_POST['proper name'], $_POST['age']); $stmt->execute(); repeat $mysqli->insert_id; $stmt->shut();                  

Bank check if Indistinguishable Entry

This is useful if you lot were to create a unique constraint on a tabular array, and then duplicates aren't allowed. You lot can even do this for multiple columns, so it volition take to exist that exact permutation. If exception handling were turned off, y'all'd check the mistake code with $mysqli->errno. With exception treatment turned on, yous could cull between that or the generic exception method $e->getCode(). Note, this differs from PDOException, which volition print the SQLSTATE, rather than the fault code.

Here's a list of error messages. The error code for a duplicate row entry from either an update or insert is 1062 and SQLSTATE is 23000. To specifically check for SQLSTATE, you must use $mysqli->sqlstate.

          try {   $stmt = $mysqli->prepare("INSERT INTO myTable (name, age) VALUES (?, ?)");   $stmt->bind_param("si", $_POST['name'], $_POST['age']);   $stmt->execute();   $stmt->shut(); } grab(Exception $eastward) {   if($mysqli->errno === 1062) echo 'Duplicate entry'; }                  

This is how y'all would set a unique constraint:

          Change TABLE myTable Add together CONSTRAINT unique_person UNIQUE (name, age)                  

Select

All select statements in parameterized queries will first off about the aforementioned. Nevertheless, there is a central difference to really storing and fetching the results. The ii methods that be are get_result() and bind_result().

get_result()

This is the more versatile of the two, as it can be used for any scenario. It should be noted that this requires mysqlnd, which has been included in PHP since five.3 and has been the default native driver since 5.iv, every bit stated here. I dubiousness many people are using older versions than that, so you lot should generally stick with get_result().

This essentially exposes the regular, non-prepared mysqli_result api. Significant, that one time y'all practice $result = get_result(), yous can employ it exactly the same way yous'd utilize $result = $mysqli->query().

At present y'all can apply the following methods for fetching 1 row at a time or all at once. Here'south but some of the most common ones, only you can take a wait at the entire mysqli_result course for all of its methods.

One Row

• $issue->fetch_assoc() - Fetch an associative array
• $result->fetch_row() - Fetch a numeric array
• $result->fetch_object() - Fetch an object array

All

• $result->fetch_all(MYSQLI_ASSOC) - Fetch an associative array
• $result->fetch_all(MYSQLI_NUM) - Fetch a numeric array

          $stmt = $mysqli->prepare("SELECT * FROM myTable WHERE proper noun = ?"); $stmt->bind_param("s", $_POST['name']); $stmt->execute(); $result = $stmt->get_result(); if($issue->num_rows === 0) exit('No rows'); while($row = $upshot->fetch_assoc()) {   $ids[] = $row['id'];   $names[] = $row['proper name'];   $ages[] = $row['age']; } var_export($ages); $stmt->shut();                  

Output:

          [22, eighteen, xix, 27, 36, 7]                  

bind_result()

Yous might be wondering, why even use bind_result()? I personally find information technology to be far inferior to get_result() in every scenario, except for when fetching a unmarried row into divide variables. Also, before get_result() existed and mysqlnd became built into PHP, this was your only option, which is why a lot of legacy lawmaking might exist using it.

The most abrasive part well-nigh using bind_result() is that y'all must bind every single column you select and and then traverse the values in a loop. This is obviously not ideal for a plethora of values or to apply with *. The star selector is especially annoying to use with bind_result(), since you don't fifty-fifty know what those values are without looking in the database. Additionally, this makes your lawmaking exceedingly unmaintainable with changes to the table. This usually won't matter, as you shouldn't be using the wildcard selector in product mode anyway (but you know you are).

          $stmt = $mysqli->prepare("SELECT id, name, age FROM myTable WHERE name = ?"); $stmt->bind_param("s", $_POST['name']); $stmt->execute(); $stmt->store_result(); if($stmt->num_rows === 0) exit('No rows'); $stmt->bind_result($idRow, $nameRow, $ageRow);  while($stmt->fetch()) {   $ids[] = $idRow;   $names[] = $nameRow;   $ages[] = $ageRow; } var_export($ids); $stmt->close();                  

Output:

          [106, 221, 3, 55, 583, 72]                  

Fetch Associative Array

I find this to be the well-nigh common use example typically. I will too be utilizing chaining in the following, though that's obviously not necessary.

          $stmt = $mysqli->prepare("SELECT id, name, historic period FROM myTable WHERE name = ?"); $stmt->bind_param("southward", $_POST['name']); $stmt->execute(); $arr = $stmt->get_result()->fetch_all(MYSQLI_ASSOC); if(!$arr) get out('No rows'); var_export($arr); $stmt->close();                  

If you need to modify the event set, and so you should probably use a while loop with fetch_assoc() and fetch each row one at a time.

          $arr = []; $stmt = $mysqli->prepare("SELECT id, proper noun, age FROM myTable WHERE name = ?"); $stmt->bind_param("s", $_POST['proper noun']); $stmt->execute(); $outcome = $stmt->get_result(); while($row = $result->fetch_assoc()) {   $arr[] = $row; } if(!$arr) get out('No rows'); var_export($arr); $stmt->close();                  

Output:

          [   ['id' => 27, 'name' => 'Jessica', 'age' => 27],    ['id' => 432, 'name' => 'Jimmy', 'age' => 19] ]                  

You lot can really practise this using bind_result() also, although it was clearly not designed for it. Hither's a clever solution, though I personally feel like it's something that's cool to know is possible, but realistically shouldn't be used.

Fetch Numeric Assortment

This follows the same format as an associative assortment. To get the entire array in one command, without a loop, you'd utilise mysqli_result->fetch_all(MYSQLI_NUM). If you lot need to fetch the results in a loop, yous must to apply mysqli_result->fetch_row().

          $stmt = $mysqli->prepare("SELECT location, favorite_color, age FROM myTable WHERE name = ?"); $stmt->bind_param("s", $_POST['name']); $stmt->execute(); $arr = $stmt->get_result()->fetch_all(MYSQLI_NUM); if(!$arr) get out('No rows'); var_export($arr); $stmt->close();                  

And of course, the while loop adaptation.

          $arr = []; $stmt = $mysqli->fix("SELECT location, favorite_color, age FROM myTable WHERE name = ?"); $stmt->bind_param("s", $_POST['name']); $stmt->execute(); $result = $stmt->get_result(); while($row = $result->fetch_row()) {   $arr[] = $row; } if(!$arr) exit('No rows'); var_export($arr); $stmt->close();                  

Output:

          [   ['Boston', 'dark-green', 28],    ['Seattle', 'blue', 49],   ['Atlanta', 'pink', 24] ]                  

Fetch Unmarried Row

I personally find it simpler to utilize bind_result() when I know for fact that I volition simply be fetching one row, every bit I tin can admission the variables in a cleaner manner.

          $stmt = $mysqli->gear up("SELECT id, name, age FROM myTable WHERE name = ?"); $stmt->bind_param("s", $_POST['name']); $stmt->execute(); $stmt->store_result(); if($stmt->num_rows === 0) exit('No rows'); $stmt->bind_result($id, $name, $age); $stmt->fetch(); echo $name; //Output: 'Ryan' $stmt->shut();                  

At present you can use just merely apply the variables in bind_result(), like $proper noun since you know they will only contain i value, not an array.

Hither's the get_result() version:

          $stmt = $mysqli->prepare("SELECT id, proper name, age FROM myTable WHERE name = ?"); $stmt->bind_param("s", $_POST['name']); $stmt->execute(); $arr = $stmt->get_result()->fetch_assoc(); if(!$arr) get out('No rows'); var_export($arr); $stmt->close();                  

You lot would and then employ the variable every bit $arr['id'] for case.

Output:

          ['id' => 36, 'name' => 'Kevin', 'age' => 39]                  

Fetch Array of Objects

This very similar to fetching an associative array. The only main difference is that you'll be accessing it similar $arr[0]->age. Also, in case yous didn't know, objects are pass by value, while arrays are past reference.

          $arr = [] $stmt = $mysqli->prepare("SELECT id, name, age FROM myTable WHERE id = ?"); $stmt->bind_param("s", $_SESSION['id']); $stmt->execute(); $result = $stmt->get_result(); while($row = $result->fetch_object()) {   $arr[] = $row; } if(!$arr) go out('No rows'); var_export($arr); $stmt->close();                  

Output:

          [   stdClass Object ['id' => 27, 'name' => 'Jessica', 'historic period' => 27],    stdClass Object ['id' => 432, 'name' => 'Jimmy', 'age' => xix] ]                  

Yous can even add property values to an existing grade as well. All the same, it should be noted that there is a potential gotcha, according to this annotate in the PHP docs. The problem is that if you take a default value in your constructor with a indistinguishable variable name, it will fetch the object first and and then gear up the constructor value, therefore overwriting the fetched event. Weirdly enough, at that place was a "bug" from PHP 5.6.21 to 7.0.6 where this wouldn't happen. Fifty-fifty though this violates principles of OOP, some people would similar this characteristic, even though it was bug in certain versions. Something like PDO::FETCH_PROPS_LATE in PDO should be implemented in MySQLi to requite you the option to cull.

          grade myClass {} $arr = []; $stmt = $mysqli->prepare("SELECT id, name, age FROM myTable WHERE id = ?"); $stmt->bind_param("due south", $_SESSION['id']); $stmt->execute(); $event = $stmt->get_result(); while($row = $upshot->fetch_object('myClass')) {   $arr[] = $row; } if(!$arr) exit('No rows'); var_export($arr); $stmt->close();                  

Every bit the comment states, this is how you would do it correctly. All you need is a simple if status to bank check if the variable equals the constructor value — if it doesn't, just don't set it in the constructor. This is essentially the same as using PDO::FETCH_PROPS_LATE in PDO.

          class myClass {   private $id;   public part __construct($id = 0) {     if($this->id === 0) $this->id = $id;   } } $arr = []; $stmt = $mysqli->prepare("SELECT id, name, age FROM myTable WHERE id = ?"); $stmt->bind_param("s", $_SESSION['id']); $stmt->execute(); $result = $stmt->get_result(); while($row = $result->fetch_object('myClass')) {   $arr[] = $row; } if(!$arr) exit('No rows'); var_export($arr); $stmt->close();                  

Another unexpected, withal potentially useful behavior of using fetch_object('myClass') is that you can modify individual variables. I'm really not sure how I feel about this, every bit this seems to violate principles of encapsulation.

Conclusion

bind_result() - all-time used for fetching single row without also many columns or *; extremely inelegant for associative arrays.

get_result() - is the preferred 1 for almost every use-example.

Like

You would probably call up that yous could exercise something like:

          $stmt = $mysqli->prepare("SELECT id, name, age FROM myTable WHERE Proper noun Like %?%");                  

But this is not allowed. The ? placeholder must exist the unabridged cord or integer literal value. This is how you lot would do information technology correctly.

          $search = "%{$_POST['search']}%"; $stmt = $mysqli->fix("SELECT id, proper name, age FROM myTable WHERE proper noun LIKE ?");  $stmt->bind_param("south", $search); $stmt->execute(); $arr = $stmt->get_result()->fetch_all(MYSQLI_ASSOC); if(!$arr) get out('No rows'); var_export($arr); $stmt->close();                  

Where In Array

This is definitely something I'd like to see improved in MySQLi. For now, using MySQLi prepared statements with WHERE IN is possible, but feels a lilliputian long-winded.

Side note: The following two examples utilise the splat operator for argument unpacking, which requires PHP 5.6+. If you lot are using a version lower than that, then y'all can substitute information technology with call_user_func_array().

          $inArr = [12, 23, 44]; $clause = implode(',', array_fill(0, count($inArr), '?')); //create three question marks $types = str_repeat('i', count($inArr)); //create 3 ints for bind_param $stmt = $mysqli->set("SELECT id, name FROM myTable WHERE id IN ($clause)"); $stmt->bind_param($types, ...$inArr); $stmt->execute(); $resArr = $stmt->get_result()->fetch_all(MYSQLI_ASSOC); if(!$resArr) go out('No rows'); var_export($resArr); $stmt->close();                  

With Other Placeholders

The get-go example showed how to employ the WHERE IN clause with dummy placeholder solely inside of information technology. What if you wanted to use other placeholders in different places?

          $inArr = [12, 23, 44]; $clause = implode(',', array_fill(0, count($inArr), '?')); //create iii question marks $types = str_repeat('i', count($inArr)); //create 3 ints for bind_param $types .= 'i'; //add 1 more int blazon $fullArr = array_merge($inArr, [26]); //merge WHERE IN array with other value(s) $stmt = $mysqli->prepare("SELECT id, name FROM myTable WHERE id IN ($clause) AND age > ?"); $stmt->bind_param($types, ...$fullArr); //4 placeholders to bind $stmt->execute(); $resArr = $stmt->get_result()->fetch_all(MYSQLI_ASSOC); if(!$resArr) leave('No rows'); var_export($resArr); $stmt->close();                  

Multiple Prepared Statements in Transactions

This might seem odd why it would fifty-fifty warrant its own section, as you tin can literally just utilise prepared statements one after another. While this will certainly work, this does non ensure that your queries are diminutive. This means that if y'all were to run 10 queries, and one failed, the other nine would nevertheless succeed. If you desire your SQL queries to execute merely if they all succeeded, and then you must apply transactions.

          effort {   $mysqli->autocommit(FALSE); //plow on transactions   $stmt1 = $mysqli->ready("INSERT INTO myTable (name, age) VALUES (?, ?)");   $stmt2 = $mysqli->prepare("UPDATE myTable SET name = ? WHERE id = ?");   $stmt1->bind_param("si", $_POST['name'], $_POST['historic period']);   $stmt2->bind_param("si", $_POST['name'], $_SESSION['id']);   $stmt1->execute();   $stmt2->execute();   $stmt1->close();   $stmt2->close();   $mysqli->autocommit(TRUE); //plow off transactions + commit queued queries } catch(Exception $due east) {   $mysqli->rollback(); //remove all queries from queue if error (undo)   throw $e; }                  

Reuse Same Template, Different Values

          try {   $mysqli->autocommit(Fake); //turn on transactions   $stmt = $mysqli->fix("INSERT INTO myTable (name, age) VALUES (?, ?)");   $stmt->bind_param("si", $proper name, $historic period);   $name = 'John';   $historic period = 21;   $stmt->execute();     $name = 'Rick';   $age = 24;   $stmt->execute();   $stmt->close();   $mysqli->autocommit(True); //turn off transactions + commit queued queries } catch(Exception $east) {   $mysqli->rollback(); //remove all queries from queue if error (undo)   throw $e; }                  

Mistake Handling

Fatal error: Uncaught Error: Call to a fellow member function bind_param() on boolean

Anyone who'south used MySQLi prepared statements has seen this message at some point, merely what does it hateful? Pretty much nothing at all. And then how exercise y'all prepare this, you might ask? To start, don't forget to turn on exception handling, instead of error handling mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT) when you create a new connection.

Exception Treatment

All of the mysqli functions render false on failure, so you could easily just cheque for truthiness on each function and written report errors with $mysqli->error. However, this is very tedious, and there's a more than elegant manner of doing this if y'all enable internal reporting. I recommend doing it this fashion, every bit it'south much more than portable from evolution to product.

This tin can be used in product besides, as long every bit y'all have an error log prepare for all errors; this needs to exist fix in the php.ini. Please don't always report errors direct on your site in product. You'll exist kicking yourself for such a silly mistake. The placement of mysqli_report() matters likewise. if you place information technology before creating a new connexion and so it volition output your password also; otherwise, it volition just written report everything after, like your queries.

Here'south what your php.ini file should expect similar in production: exercise both display_errors = Off and log_errors = On . Also, keep in heed that each page should really only exist using a single, global, try/take hold of block, rather than wrapping each query individually. The simply exception to this is with transactions, which would be nested, just throw its own exception, so the global try/catch tin can "catch" it.

          try {   $stmt = $mysqli->fix("DELETE FROM myTable WHERE id = ?");   $stmt->bind_param("i", $_SESSION['id']);   $stmt->execute();   $stmt->close();    $stmt = $mysqli->prepare("SELECT id, proper name, age FROM myTable WHERE name = ?");   $stmt->bind_param("s", $_POST['name']);   $stmt->execute();   $arr = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);   $stmt->shut();    effort {     $mysqli->autocommit(FALSE); //plow on transactions     $stmt = $mysqli->prepare("INSERT INTO myTable (name, age) VALUES (?, ?)");     $stmt->bind_param("si", $proper name, $age);     $proper name = 'John';     $age = 21;     $stmt->execute();       $name = 'Rick';     $historic period = 24;     $stmt->execute();     $stmt->close();     $mysqli->autocommit(TRUE); //turn off transactions + commit queued queries   } take hold of(Exception $east) {     $mysqli->rollback(); //remove all queries from queue if error (disengage)     throw $e;   }   } catch (Exception $eastward) {   error_log($east);   exit('Mistake bulletin for user to sympathize'); }                  

Custom Exception Handler

As stated earlier, you can alternatively utilise set_exception_handler() on each page (or a global redirect). This gets rid of the layer of curly brace nesting. If y'all are using transactions, you should all the same utilise a endeavour catch with that, merely then throw your own exception.

          set_exception_handler(function($e) {   error_log($e);   exit('Error deleting'); }); $stmt = $mysqli->fix("DELETE FROM myTable WHERE id = ?"); $stmt->bind_param("i", $_SESSION['id']); $stmt->execute(); $stmt->close();                  

Gotcha with Exception Handling

You lot'd wait for all MySQLi errors to be converted to exceptions with mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT). Oddly enough, I noticed that it still gave me a warning error when bind_param() had besides many or also little bound variables or types. The bulletin outputted is as follows:

Warning: mysqli_stmt::bind_param(): Number of variables doesn't friction match number of parameters in prepared argument

A solution to this is to utilise a global error handler to trigger an exception. An example of this could exist:

          set_error_handler(function($errno, $errstr, $errfile, $errline) {   throw new Exception("$errstr on line $errline in file $errfile"); });                  

This only happened on runtime warnings, but I converted all errors to exceptions. I see no problem doing this, but in that location are some people who are strongly against it.

Do I Demand $stmt->close()?

Great question. Both $mysqli->close() and $stmt->shut() essentially have the same upshot. The old closes the MySQLi connection, while the latter closes the prepared argument. TLDR; both are really generally non even necessary in most cases, since both will close once the script's execution is complete anyway. There's besides a function to but free the memory associated with the MySQLi result and prepared statement, respectively: $event->gratis() and $stmt->costless(). I myself, will probable never utilize it, but if you're interested, here'south the one for the result and for the the parameterized query. The post-obit should also exist noted: both $stmt->shut() and the terminate of the execution of the script will the gratis upwardly the memory anyhow.

Terminal verdict: I commonly just exercise $mysqli->shut() and $stmt->close(), even though it can be argued that it's a lilliputian superfluous. If you are planning on using the aforementioned variable $stmt again for some other prepared statements, and so you must either shut information technology, or use a different variable name, like $stmt2. Lastly, I have never found a need to just free them, without closing them.

Classes: mysqli vs. mysqli_stmt vs. mysqli_result

Ane thing y'all may have realized along the manner is that there are certain methods that be in two of the classes, like an alias almost. I personally believe information technology would be better to only have one version, like in PDO, to avert confusion.

• mysqli::$affected_rows or mysqli_stmt::$affected_rows - Belongs to mysqli_stmt. Works the same with either, merely will exist an fault if called after the statement is closed with either method
• mysqli_result::$num_rows or mysqli_stmt::$num_rows - $consequence->num_rows can only be used with get_result(), while $stmt->num_rows can only be used with bind_result().
• mysqli::$insert_id or mysqli_stmt::$insert_id - Belongs to mysqli. Ameliorate to use $mysqli->insert_id, since it will still work even afterwards $stmt->shut() is used. In that location's also a note on the PHP docs from 2011 stating that $stmt->insert_id will just get the offset executed query. I tried this on my current version of 7.1 and this doesn't seem to exist the instance. The recommended one to use is the mysqli class version anyway.

So Using Prepared Statements Means I'm Safe From Attackers?

While yous are rubber from SQL injection, you still demand validate and sanitize your user-inputted information. You can utilize a function like filter_var() to validate before inserting information technology into the database and htmlspecialchars() to sanitize afterward retrieving information technology.

Firmly believes that web technologies should take over everything. Enjoys writing tutorials nigh JavaScript and PHP.

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Source: https://websitebeaver.com/prepared-statements-in-php-mysqli-to-prevent-sql-injection

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