Why has my PHP system() command stopped returning output to my scripts ... i used to work!

Question

I have a PHP script that calls a .bat file using system(). The output is written to the screen and I derive some values from parsing this output. This is running on windows 2003 IIS server. PHP v5.2.0

Specifically I am using this script to launch an Amazon EC2 instance and assign an IP address to it. It has worked great for me so far but recently the problem started.

Here is the code

$resultBatTemp = system("cmd /C C:\Inetpub\ec2\my_batch_file_to_launch_instance.bat");
$resultBat = (string)$resultBatTemp;
$instanceId  = substr($resultBat, 9, 10);

...

Once I have this instace Id I can run another batch file that calls associates an ip address with this instance. It would appear that the instance does get launched but I never get the output on the screen.

For some reason this has all stopped working, the page freezes and never refreshes. I also need to completely exit safari or mozilla otherwise all pages from the website fail to load. Only when I relaunch the browser can i view the website again. I've connected to the webserver that hosts these scripts and checked PHP error log but nothing shows there. I've opened a DOS prompt and entered the code from the bat file that way and it connects to amazon and launches the instance fine. Ive isolated this bit of code and removed the system command and the rest of the script runs fine, so it appears that the hold up is with outputting the results of the bat file.

Recently I have purchased a new domain name for the site so this script is running from this domain. Might this cause the problem?

thanks

------------------------------------------------UPDATE-----------------------------------------------

Well hope this helps someone, I didnt find out what was wrong but created a new PHP file with a simple system command that called a .bat file, and a non-existent .bat file expecting to get an error back but nothing - just the usual hang for ages. So I restarted IIS and this fixed the problem. Dont know what was wrong but that did the trick.

Answer 1

Maybe first check what the system() call returns. According to documentation it will return FALSE in case of failure. Also, including your my_batch_file_to_launch_instance.bat in the question might help in solving it.

Answer 2

Try using the passthru function

Also make sure that all your commands are safe use escapeshellarg() or escapeshellcmd() to ensure that users cannot trick the system into executing arbitrary commands.