What are some common mistakes developers make when using PHP to validate input fields, and how can they be avoided?

One common mistake is not properly sanitizing user input before validating it, which can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To avoid this, always sanitize user input using functions like `htmlspecialchars` or `mysqli_real_escape_string` before validating it. 

// Sanitize user input before validating
$user_input = htmlspecialchars($_POST['user_input']);

// Validate the sanitized input
if (strlen($user_input) < 5) {
    echo "Input must be at least 5 characters long";
} else {
    echo "Input is valid";
}

Keywords

SQL injection XSS attacks filter_var htmlspecialchars validation errors

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