PHP Exec Won't Launch Executables

It looks like you are:

• on Windows
• trying to launch an external program asynchronously

Here is the secret sauce that will allow you to do so:

function async_exec_win($cmd)
{
    $wshShell = new COM('WScript.Shell');
    $wshShell->Run($cmd, 0, false); // NB: the second argument is meaningless
                                    // It just has to be an int <= 10
}

This requires the COM class to be available to your PHP instance, you may need to enable extension=php_com_dotnet.dll in php.ini (since PHP 5.3.15/5.4.5) in order to make it available.

Also note that this will require a full file name of the file you wish to execute, as the extension search list will not be used outside cmd.exe. So instead of srcds -console ... you'll want srcds.exe -console ... - personally I don't like the chdir() approach, I'd rather pass the full path of the exe into the function instead - but if you do this, you'll need to make sure the directory separators are of the correct type for the operating system. PHP will let you use whatever you like wherever you like, the OS won't be so forgiving.

For completeness, here's how to do a similar thing on *nix. This is actually better than the Windows version as it also returns the PID of the process that was created:

function async_exec_unix($cmd)
{
    return (int) exec($cmd . ' > /dev/null 2>&1 & echo $!');
}

Something to pay attention to: your command must be properly escaped. Neither of these implementations perform any validation on the command being executed, they just run it blindly. Never pass user input to an external program without escaping it as appropriate to the host operating system!