What are common mistakes made when writing PHP code?

One common mistake when writing PHP code is not properly sanitizing user input, which can lead to security vulnerabilities like SQL injection or cross-site scripting attacks. To solve this issue, always use functions like `mysqli_real_escape_string()` or prepared statements to sanitize user input before using it in database queries. 

// Sanitize user input using mysqli_real_escape_string()
$user_input = mysqli_real_escape_string($connection, $_POST['user_input']);

// Use the sanitized input in a database query
$query = "SELECT * FROM users WHERE username='$user_input'";
$result = mysqli_query($connection, $query);

Keywords

syntax errors undefined variables SQL injection XSS vulnerabilities inefficient code

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