Cannot send headers; headers already sent in , line 0

Yesterday, I started upgrading a test server to Apache 2.2 and PHP 5.2.9 and ran into this is a problem, which then bugged me for a good day. So here’s the run down:

My test.php:

<?php
ob_start();
system('file -i -b /path/file.txt');
$contents = ob_get_contents();
ob_end_clean();
var_dump(headers_sent($file, $line), $file, $line);

My test2.php:

<?php
$contents = shell_exec('file -i -b /path/file.txt');
$contents = trim($contents);
var_dump(headers_sent($file, $line), $file, $line);

test.php claims that headers were send, while test2.php shows the expected behavior. The difference is not only system() vs. shell_exec(). But the ob_start(). Apparently headers_sent() returns true right after system() was called. We’ve used output buffering to trap whatever came back from system and this works on PHP 5.2.6 and 5.2.8, but not on 5.2.9.

Since I was after the response of the shell call, using shell_exec() is what should have been used to begin with — still. This is pretty weird.

Update: I’ve opened #47973 - Yay, bug fixed!