How can I prevent SQL injection in PHP?

SQL injection is a type of security vulnerability that occurs when an attacker is able to manipulate an SQL query, often by inputting malicious code through user input. This can lead to unauthorized access to the database and potentially compromising sensitive information. However, there are several measures that can be taken in PHP to prevent SQL injection and ensure that user input is properly sanitized and validated.

1. Use Prepared Statements with Parameterized Queries

Prepared statements provide a way to separate the data from the SQL logic, allowing the database to distinguish between code and data. This prevents any malicious code entered by the user from being executed as SQL commands. Here's an example of how to use prepared statements with PDO (PHP Data Objects):

$pdo = new PDO("mysql:host=localhost;dbname=mydb", $username, $password);
$stmt = $pdo->prepare("INSERT INTO table (column) VALUES (:value)");
$stmt->bindParam(':value', $userInput);

2. Use Prepared Statements with Stored Procedures

Stored procedures are a powerful tool to prevent SQL injection as they allow you to define specific SQL logic that can be executed with parameters, similar to prepared statements. The difference is that stored procedures are stored on the database server itself, reducing the need for dynamic SQL. Here's an example of how to use prepared statements with stored procedures in PHP:

$pdo = new PDO("mysql:host=localhost;dbname=mydb", $username, $password);
$stmt = $pdo->prepare("CALL insertData(?)");
$stmt->bindParam(1, $userInput);

3. Use a Database Abstraction Layer

A database abstraction layer is a software component that provides an abstract interface to interact with different databases. These libraries often have built-in methods to sanitize and escape user input to prevent SQL injection. Examples of popular database abstraction layers for PHP include Doctrine and Laravel's Eloquent.

4. Sanitize and Validate User Input

Another effective way to prevent SQL injection is to sanitize and validate user input before using it in an SQL query. This involves removing any potentially harmful characters or escaping them properly. PHP provides several built-in functions for sanitizing user input, such as htmlspecialchars() and filter_var(). It's important to combine input sanitization with input validation to ensure that the input matches the expected format.

5. Implement Least Privilege Principle

The least privilege principle states that every user should have the minimum level of access required to perform their tasks. In the context of SQL injection prevention, this means creating separate database user accounts with limited privileges. This way, even if an SQL injection attack succeeds, the attacker will only have access to a limited set of data or functionalities.


SQL injection is a serious security vulnerability that can lead to unauthorized access and data breaches. However, by implementing the measures mentioned above, such as using prepared statements, using a database abstraction layer, sanitizing and validating user input, and implementing the least privilege principle, you can greatly reduce the risk of SQL injection attacks in your PHP applications.