How can PHP developers effectively sanitize and validate user input to prevent security vulnerabilities in a web application?

To prevent security vulnerabilities in a web application, PHP developers should sanitize and validate user input to prevent SQL injection, cross-site scripting (XSS), and other attacks. This can be done by using functions like htmlspecialchars() to sanitize user input and by validating input against expected formats using functions like filter_var(). 

// Sanitize user input using htmlspecialchars()
$clean_input = htmlspecialchars($_POST['user_input'], ENT_QUOTES, 'UTF-8');

// Validate user input against expected format
if (filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
    // Input is a valid email address
} else {
    // Input is not a valid email address
}

Keywords

filter_input htmlspecialchars validation SQL injection cross-site scripting

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