Description:
------------
A call to error_log may result in data being output before the headers, thereby corrupting the response.

The same doesn't happen with other PHP output functions.

The ini directive error_log is set to "no value". The docs say "If this directive is not set, errors are sent to the SAPI error logger".

Test script:
---------------
<?php
error_log("oops");
echo "content";
inexistent_function(); //fatal; no problem


Expected result:
----------------
X-Powered-By: PHP/5.3.3
Content-type: text/html

oops
content<br />
<b>Fatal error</b>:  Call to undefined function inexistent_function() in <b>/home/glopes/test.php</b> on line <b>4</b><br />


Actual result:
--------------
$ /opt/php5/bin/php-cgi test.php
oops
X-Powered-By: PHP/5.3.3
Content-type: text/html

content<br />
<b>Fatal error</b>:  Call to undefined function inexistent_function() in <b>/home/glopes/test.php</b> on line <b>4</b><br />