How to print all information from an HTTP request to the screen, in PHP

Nobody mentioned how to dump HTTP headers correctly under any circumstances.

From CGI specification rfc3875, section 4.1.18:

Meta-variables with names beginning with "HTTP_" contain values read from the client request header fields, if the protocol used is HTTP. The HTTP header field name is converted to upper case, has all occurrences of "-" replaced with "" and has "HTTP" prepended to give the meta-variable name.

foreach ($_SERVER as $key => $value) {
    if (strpos($key, 'HTTP_') === 0) {
        $chunks = explode('_', $key);
        $header = '';
        for ($i = 1; $y = sizeof($chunks) - 1, $i < $y; $i++) {
            $header .= ucfirst(strtolower($chunks[$i])).'-';
        }
        $header .= ucfirst(strtolower($chunks[$i])).': '.$value;
        echo $header.'<br>';
    }
}

Details: http://cmyker.blogspot.com/2012/10/how-to-dump-http-headers-with-php.html

A simple way would be:

<?php
print_r($_SERVER);
print_r($_POST);
print_r($_GET);
print_r($_FILES);
?>

A bit of massaging would be required to get everything in the order you want, and to exclude the variables you are not interested in, but should give you a start.

Well, you can read the entirety of the POST body like so

echo file_get_contents( 'php://input' );

And, assuming your webserver is Apache, you can read the request headers like so

$requestHeaders = apache_request_headers();

Lastly:

print_r($_REQUEST);

That covers most incoming items: PHP.net Manual: $_REQUEST