PHP Proxy for JSON with wildcard CORS

proxy.php

<?php
    header('Access-Control-Allow-Origin: *');
    header("Content-Type: application/json; charset=utf-8");
    
    $url = htmlspecialchars($_GET['url']);
    
    if ($url) {
    	$content = file_get_contents($url);
    } else {
    	$content = 'error';
    }
    
    echo json_encode(json_decode($content), JSON_PRETTY_PRINT);
?>