What are some best practices for allowing user input on PHP-generated HTML pages?

When allowing user input on PHP-generated HTML pages, it is important to sanitize and validate the input to prevent security vulnerabilities such as SQL injection or cross-site scripting attacks. One best practice is to use PHP functions like htmlentities() or htmlspecialchars() to escape user input before displaying it on the page. Additionally, validating user input against expected formats or using filters like filter_var() can help ensure the data is safe to use. 

// Example of sanitizing and validating user input in PHP
$userInput = $_POST['user_input'];

// Sanitize user input using htmlentities()
$sanitizedInput = htmlentities($userInput);

// Validate user input using filter_var() with FILTER_VALIDATE_EMAIL
if (filter_var($userInput, FILTER_VALIDATE_EMAIL)) {
    echo "Valid email address: " . $sanitizedInput;
} else {
    echo "Invalid email address";
}

Keywords

XSS prevention htmlentities htmlspecialchars input validation filter_input

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