What syntax considerations should be kept in mind when writing PHP code for form validation and output display?

When writing PHP code for form validation and output display, it is important to properly sanitize user input to prevent security vulnerabilities such as SQL injection or cross-site scripting attacks. Additionally, it is crucial to validate user input to ensure it meets the expected format or criteria. Finally, when displaying output, remember to escape any user-generated content to prevent HTML injection. 

// Example of sanitizing user input
$unsafe_input = $_POST['input'];
$safe_input = htmlspecialchars($unsafe_input);

// Example of validating user input
$email = $_POST['email'];
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // Email is valid
} else {
    // Email is not valid
}

// Example of escaping user-generated content
$user_content = "<script>alert('XSS attack');</script>";
$escaped_content = htmlspecialchars($user_content);
echo $escaped_content;

Keywords

PHP form validation syntax output display error handling

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