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PHP Filters

PHP provides a set of built-in functions to filter and validate data. Filters can be used to sanitize user input, ensuring that it meets specific criteria before processing.

Using Filters

<?php
$email = "user@example.com";
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Valid email address.";
} else {
    echo "Invalid email address.";
}
?>

Explanation: This example uses filter_var() with FILTER_VALIDATE_EMAIL to validate an email address.

Sanitizing Input

<?php
$input = "<script>alert ('Hi');</script>";
$sanitized_input = filter_var($input, FILTER_SANITIZE_STRING);

echo $sanitized_input;
?>

Explanation: This example sanitizes a string by removing any HTML tags using FILTER_SANITIZE_STRING.

Common Filters

Here are some commonly used filters in PHP:

  • FILTER_VALIDATE_EMAIL: Validates an email address.
  • FILTER_VALIDATE_URL: Validates a URL.
  • FILTER_SANITIZE_STRING: Removes HTML tags from a string.
  • FILTER_SANITIZE_EMAIL: Sanitizes an email address.
  • FILTER_SANITIZE_URL: Sanitizes a URL.

Example of Validating a URL

<?php
$url = "https://www.example.com";
if (filter_var($url, FILTER_VALIDATE_URL)) {
    echo "Valid URL.";
} else {
    echo "Invalid URL.";
}
?>

Explanation: This example checks if a URL is valid using FILTER_VALIDATE_URL.

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