[Icecast] URL authentication not working

[infoweb1 at crobiz.com]

Icecast 2.4.1 and 2.4.2, OS: CentOS 6.6 x64

Tried to install icecast using following two different methods described in these links:
(1) http://www.ukhost4u.co.uk/blog/538/install-icecast-2-centos-6-server/
(2) https://www.servint.net/university/article/taking-the-chill-out-of-installing-icecast/

Both of these resulted in working and stable icecast, but without the possibility of url authentication. 

Mountpoint authentication is configured as shown here:
<authentication type="url">
<option name="mount_add"       value="http://some.server.org/stream_control.php"/>
<option name="mount_remove"    value="http://some.server.org/stream_control.php"/>
<option name="listener_add"    value="http://some.server.org/stream_control.php"/>
<option name="listener_remove" value="http://some.server.org/stream_control.php"/>
<option name="stream_auth" value="http://some.server.org/stream_control.php"/>
<option name="user" value='source'/>
<option name="pass" value='pass'/>
<option name="auth_header" value="icecast-auth-user: 1"/>
</authentication>

Script named stream_control.php just writes POST data received from calling site (to some file) and returns icecast-auth-user: 1.

This script is never called by any of these methods by the icecast server, also in the error.log I am able to find following lines (every time I try to connect to icecast as a listener - or a stream client):

INFO auth/auth_add_listener adding client for authentication
INFO auth/queue_auth_client auth on /mountpoint has 1 pending
INFO auth_url/url_add_listener client auth (http://some.server.org/stream_control.php) failed with ""

Please advise further actions. Thanks!

PS: yum update was done, without any change.
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