What are common mistakes to avoid when using jQuery in PHP applications?

One common mistake to avoid when using jQuery in PHP applications is not properly escaping user input before using it in jQuery functions. This can lead to security vulnerabilities such as cross-site scripting (XSS) attacks. To prevent this, always sanitize and escape user input using functions like htmlspecialchars() before passing it to jQuery functions.

// Sanitize and escape user input before using it in jQuery functions
$user_input = $_POST['user_input'];
$escaped_input = htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');

// Pass the sanitized input to a jQuery function
echo "<script>";
echo "$(document).ready(function() {";
echo "  var userInput = '" . $escaped_input . "';";
echo "  // Use userInput in jQuery functions";
echo "});";
echo "</script>";