What are the key considerations when validating and escaping variables in SQL statements in PHP?

When validating and escaping variables in SQL statements in PHP, it is crucial to prevent SQL injection attacks by sanitizing user input. This involves validating the input to ensure it meets expected criteria and escaping it to prevent malicious characters from being executed as SQL commands. 

// Validate and escape variables in SQL statements
$user_input = $_POST['user_input']; // Example user input from a form

// Validate the input
if (!empty($user_input)) {
    // Escape the input to prevent SQL injection
    $escaped_input = mysqli_real_escape_string($connection, $user_input); // $connection is your database connection object
    // Use the escaped input in your SQL query
    $query = "SELECT * FROM users WHERE username = '$escaped_input'";
    $result = mysqli_query($connection, $query);
}

Keywords

SQL injection mysqli_real_escape_string prepared statements PDO input validation

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