Question about warning generated by script

Hello;
This script line is generating a warning, but It doesn't really say what the problem is. 
The warning is "Warning:  file_put_contents(<contents of the file truncated>&...)<path to script file and line number>"

Is this too much to put in one line like this?

file_put_contents(str_replace('_LAB_LABEL', '_'.strtoupper($_labName), file_get_contents(self::$_labTemplate)), $_labName."/index.php");

Thanks for time and attention;
JK