How can placeholders in SQL queries help prevent SQL injection vulnerabilities?

SQL injection vulnerabilities can occur when user input is directly concatenated into SQL queries, allowing malicious users to manipulate the query and potentially access or modify sensitive data. By using placeholders in SQL queries, input values are treated as data rather than executable code, preventing SQL injection attacks. 

// Using placeholders in SQL queries to prevent SQL injection vulnerabilities
$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');

// User input
$userInput = $_POST['user_input'];

// Prepare a SQL statement with a placeholder
$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username');

// Bind the user input to the placeholder
$stmt->bindParam(':username', $userInput);

// Execute the prepared statement
$stmt->execute();

// Fetch the results
$results = $stmt->fetchAll();

// Process the results
foreach($results as $row) {
    // Do something with the data
}

Keywords

PHP SQL injection placeholders prepared statements security

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