Chrome记录器无法使用PHP输出

I'm not getting debug output. I do have the extension enabled.

PHP ('upload.php'):

include '/opa/ChromePhp.php'; //Wrong path maybe, I already tried just 'ChromePhp.php'?
ChromePhp::log('Hello console!');
ChromePhp::log($_SERVER);
ChromePhp::warn('something went wrong!');

JS (inside 'index.html'):

function uploadText(text) {
    var data = new FormData();
    data.append("data" , text);
    var xhr = (window.XMLHttpRequest) ? new XMLHttpRequest() : new activeXObject("Microsoft.XMLHTTP");
    xhr.open( 'post', '/opa/upload.php', true );
    xhr.send(data);
}

Chrome console with XHR logging enabled:

Chrome network tab: (It isn't loading ChromePhp, right, or could it be invisible for the client?)

File structure (these files are in "/domains/degeneracy.nl/public_html/opa/"):