What are the security considerations when outputting data from a database in PHP, and how can SQL injection vulnerabilities be mitigated?

When outputting data from a database in PHP, it is important to sanitize the data to prevent SQL injection vulnerabilities. This can be achieved by using prepared statements with parameterized queries, which separate SQL code from user input. By binding parameters to placeholders in the SQL query, the database engine can distinguish between code and data, effectively preventing malicious input from altering the query. 

// Establish a database connection
$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');

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

// Bind a parameter to the placeholder
$stmt->bindParam(':username', $_GET['username']);

// Execute the query
$stmt->execute();

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

// Output the data
foreach ($results as $row) {
    echo $row['username'] . '<br>';
}

Keywords

SQL injection database output security considerations PHP functions vulnerabilities

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