PHP exec on another PHP file - How do I get my script to wait?

I'm running a continuous PHP loop that executes another PHP file by using exec("php ...");. The plan is for the executed script to run, then sleep for 2 seconds, then start again. However, it seems like my loop is starting a new instance every 2 seconds instead. So long question short, how do I get my first php script to wait until the execution of script nr 2 is complete?

All this is run using the command line. I would also like the echo functions in script nr 2 to show up on the command line.

Any thoughts would help.


Exec does not maintain any state information between instances. You could:
Loop in your subscript
You could set some sort of environment variables or that are read at the beginning of the subscript and written at the end.
You could have the subscript read/write to a file in a similar fashion
You could pass in parameters to the subscript who's output is captured

For outputting to the screen, you might play around with the other exec/system calls:

I believe passthru() will work. Another possibility if it doesn't is to call exec(), using the output parameters to capture the output strings from the subscript. Then just echoing that output on return of the subscript.

I also believe that using the output parameters (or capturing the result of the function in a variable) will cause the exec to wait until the command is complete before continuing on.