Simple PHP proxy script

proxy.php

<?php

$url = 'https://httpbin.org/anything?';

function proxyDoHeader($curl, $headerLine)
{
    $trimmed = trim($headerLine);
    if (strlen($trimmed) > 0 && !preg_match('/^(Date|Server|Transfer)/', $trimmed)) {
        header($trimmed);
    }

    return strlen($headerLine);
}

foreach ($_GET as $key => $value) {
    $url .= sprintf('%s=%s&', $key, urlencode($value));
}

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADERFUNCTION, 'proxyDoHeader');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);

$headers = array();

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    curl_setopt($ch, CURLOPT_POST, 1);

    if (!empty($_SERVER['CONTENT_TYPE']) &&
        $_SERVER['CONTENT_TYPE'] === 'application/json'
    ) {
        $headers[] = 'Content-Type: ' . $_SERVER['CONTENT_TYPE'];
        $json = file_get_contents('php://input');
        curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
    } else {
        $headers[] = 'Content-Type: application/x-www-form-urlencoded';
        $postFields = '';
        foreach ($_POST as $key => $value) {
            $postFields .= sprintf('%s=%s&', $key, urlencode($value));
        }
        curl_setopt($ch, CURLOPT_POSTFIELDS, $postFields);
    }
}

curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

$contents = curl_exec($ch);
curl_close($ch);

echo($contents);