Return code 127 when calling php from C

[curacao]

I'm running a php script by calling it form a C-program as one would call it from the command line.

/usr/bin/php -q /scriptdir/script.php

This works most of the time, but sometimes is fails and returns 127 as the return code. I have not been able to work out why this is, can anyone help?

[skripty]

i suggest you find out what the return code means and see if you can understand the reason for the code and then try and work out why.

[curacao]

I understood it meant that it couldn't execute the (php) command. So it doesn't tell me much. The puzzling thing is that it works normally most of the time but fails sometimes. Even when it's called again within seconds of a failed call it works again.