Response header disappears with Angular

Question

I'm trying to get Chrome Logger working in an Angular app running against a PHP backend, but for some reason the X-ChromeLogger-Data header doesn't seem to be coming through when the API is accessed by the Angular app.

If I open the API's access point directly or hit it with a jQuery.get() request everything works fine, even if I make the ajax request from another domain. The API also works correctly otherwise, even when used by the Angular app. It's just that one header disappears somewhere along the way. It doesn't even appear in Chrome's console.

What could cause a header to disappear?

Here's a request made with jQuery.get()

Request:
GET /?action=load HTTP/1.1
Host: -
Connection: keep-alive
Accept: application/json, text/javascript, */*; q=0.01
Origin: -
X-FirePHP-Version: 0.0.6
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.80 Safari/537.36
Referer: -
Accept-Encoding: gzip, deflate, sdch
Accept-Language: fi-FI,fi;q=0.8,en-US;q=0.6,en;q=0.4,sv;q=0.2

Response:
HTTP/1.1 200 OK
Date: Sat, 07 Nov 2015 10:41:22 GMT
Server: Apache/2.4.12 (Ubuntu)
X-Powered-By: PHP/5.6.11-1ubuntu3.1
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, OPTIONS, PUT, DELETE
Access-Control-Allow-Headers: Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control, X-ChromeLogger-Data
X-ChromeLogger-Data: eyJ2ZXJzaW9uIjoiNC4wIiwiY29sdW1ucyI6WyJsYWJlbCIsImxvZyIsImJhY2t0cmFjZSIsInR5cGUiXSwicm93cyI6W1siQVBJIiwiQVBJIHJlYWNoZWQiLCJ1bmtub3duIiwid2FybiJdXSwicmVxdWVzdF91cmkiOiJcLz9hY3Rpb249bG9hZCJ9
Content-Length: 15
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8

And here's one from the Angular app:

Request:
GET /?action=load HTTP/1.1
Host: -
Connection: keep-alive
Accept: application/json, text/plain, */*
Origin: -
X-FirePHP-Version: 0.0.6
User-Agent: Mozilla/5.0 (Linux; U; Android 4.0; en-us; GT-I9300 Build/IMM76D) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30
Referer: -
Accept-Encoding: gzip, deflate, sdch
Accept-Language: fi-FI,fi;q=0.8,en-US;q=0.6,en;q=0.4,sv;q=0.2

Response:
HTTP/1.1 200 OK
Date: Sat, 07 Nov 2015 10:34:33 GMT
Server: Apache/2.4.12 (Ubuntu)
X-Powered-By: PHP/5.6.11-1ubuntu3.1
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, OPTIONS, PUT, DELETE
Access-Control-Allow-Headers: Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control, X-ChromeLogger-Data
Content-Length: 15
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8

The Angular code used to make the above request:

$http.get( endpoint, { params : { action : 'load' } } ).then(
    function( response ) {
        console.log( response );
    },
    function() {
        console.log( 'fail' );
    }
);

Answer 1

After Dvir's tip to further inspect the differences between the requests (with the aid of Fiddler) I finally manager to solve the problem. I was running the Angular app with Chrome's mobile device simulator turned on, and it turns out the Monolog ChromePHPHandler requires for the text "Chrome" to be present in the User-Agent header, which it wasn't when the simulator was turned on.