Sanitizing User Input
When you build web applications that accept user input, you must be aware of the security risks that come with handling data from outside sources. One of the most common threats is cross-site scripting (XSS), where an attacker tries to inject malicious scripts through form fields. If you display user input directly on your website without sanitizing it, you risk letting attackers execute harmful code in your users' browsers.
sanitize_input.php
1234567891011121314151617<?php // Assume this script processes form input sent via POST // Retrieve raw user input $raw_username = $_POST['username'] ?? ''; $raw_email = $_POST['email'] ?? ''; // Sanitize username for HTML output to prevent XSS $safe_username = htmlspecialchars($raw_username, ENT_QUOTES, 'UTF-8'); // Sanitize email using filter_var $safe_email = filter_var($raw_email, FILTER_SANITIZE_EMAIL); // Output sanitized values echo "Hello, " . $safe_username . "!<br>"; echo "Your sanitized email is: " . $safe_email; ?>
Sanitization is the process of cleaning user input to ensure it cannot be used for malicious purposes. In PHP, functions like htmlspecialchars convert special characters in user input to HTML entities, making it safe to display on a page. For example, if a user enters a string with angle brackets (< or >), htmlspecialchars will convert them so they are shown as plain text, not interpreted as HTML or JavaScript. Similarly, filter_var can be used to sanitize and validate different types of input, such as email addresses, URLs, and numbers.
By always sanitizing user input before displaying it or using it in your application, you reduce the risk of security vulnerabilities and protect both your website and its users.
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When you build web applications that accept user input, you must be aware of the security risks that come with handling data from outside sources. One of the most common threats is cross-site scripting (XSS), where an attacker tries to inject malicious scripts through form fields. If you display user input directly on your website without sanitizing it, you risk letting attackers execute harmful code in your users' browsers.
sanitize_input.php
1234567891011121314151617<?php // Assume this script processes form input sent via POST // Retrieve raw user input $raw_username = $_POST['username'] ?? ''; $raw_email = $_POST['email'] ?? ''; // Sanitize username for HTML output to prevent XSS $safe_username = htmlspecialchars($raw_username, ENT_QUOTES, 'UTF-8'); // Sanitize email using filter_var $safe_email = filter_var($raw_email, FILTER_SANITIZE_EMAIL); // Output sanitized values echo "Hello, " . $safe_username . "!<br>"; echo "Your sanitized email is: " . $safe_email; ?>
Sanitization is the process of cleaning user input to ensure it cannot be used for malicious purposes. In PHP, functions like htmlspecialchars convert special characters in user input to HTML entities, making it safe to display on a page. For example, if a user enters a string with angle brackets (< or >), htmlspecialchars will convert them so they are shown as plain text, not interpreted as HTML or JavaScript. Similarly, filter_var can be used to sanitize and validate different types of input, such as email addresses, URLs, and numbers.
By always sanitizing user input before displaying it or using it in your application, you reduce the risk of security vulnerabilities and protect both your website and its users.
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