<?php

/**

* Sanitizes JSON input to prevent potential vulnerabilities.

*

* This function takes a JSON string as input and sanitizes it to remove

* potentially harmful characters or structures. It's designed for testing

* and should not be considered a comprehensive security solution for production

* environments.

*

* @param string $json_string The JSON string to sanitize.

* @return string|null The sanitized JSON string, or null if sanitization fails.

*/

function sanitizeJson(string $json_string): ?string

{

// Remove potentially harmful characters. This is a basic example;

// consider a more comprehensive character filtering approach for production.

$sanitized_string = preg_replace('/[<>&"\'\\]/', '', $json_string);

// Validate the JSON structure. This prevents invalid JSON from being processed.

$decoded = json_decode($sanitized_string);

if (json_last_error() !== JSON_ERROR_NONE) {

// JSON decoding failed. Return null to indicate an error.

error_log("JSON decoding error: " . json_last_error_msg()); // Log the error

return null;

}

// If decoding was successful, return the original JSON string.

return $sanitized_string;

}

// Example usage (for testing)

$test_json = '{ "name": "John Doe", "age": 30, "city": "New York" , "description": "This is a test" }';

$sanitized_json = sanitizeJson($test_json);

if ($sanitized_json !== null) {

echo "Sanitized JSON:\n";

echo $sanitized_json . "\n";

} else {

echo "Sanitization failed.\n";

}

// Example with potentially malicious input

$malicious_json = '{"name": "Test <script>alert(\'XSS\')</script>"}';

$sanitized_malicious_json = sanitizeJson($malicious_json);

if ($sanitized_malicious_json !== null) {

echo "Sanitized Malicious JSON:\n";

echo $sanitized_malicious_json . "\n";

} else {

echo "Sanitization failed.\n";

}

?>