How to parse stderr from a child process

[php_saved_me]

Hello, I'm executing an external process using 'proc_open'. I'd like to catch a specific error from the external process (error: 'unsupported codec'), but I can't conceptualize what's going on. How can I determine if the 'unsupported codec' error has occured from within my php script? Thanks!

[php_saved_me]

I've figured it out:

$error_out = stream_get_contents($pipes[2]);
if (strpos($error_out, 'Unsupported codec')) {
  //do something
}