What best practices should be followed when handling user input in PHP to prevent SQL injection vulnerabilities?

To prevent SQL injection vulnerabilities when handling user input in PHP, it is best practice to use prepared statements with parameterized queries. This approach separates the SQL query logic from the user input data, preventing malicious SQL code from being executed. Additionally, input validation and sanitization should be implemented to further secure the application. 

// Example of using prepared statements to prevent SQL injection
$mysqli = new mysqli("localhost", "username", "password", "database");

// Check connection
if ($mysqli->connect_error) {
    die("Connection failed: " . $mysqli->connect_error);
}

// Prepare a SQL query with a parameter
$stmt = $mysqli->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);

// Set the parameter value and execute the query
$username = $_POST['username'];
$stmt->execute();

// Process the results
$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    // Handle the user data
}

// Close the statement and connection
$stmt->close();
$mysqli->close();

Keywords

SQL injection user input validation prepared statements PDO escaping data

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