title: php command line on windows
body: <p>I'm using <code>php</code> on <code>WAMP</code>. 
  I'm trying to run an external program prog.exe under directory abc which takes one numeric parameter. 
  the following command on DOS command line works fine</p>
  
  <pre><code>c:\abc\prog.exe 1234
  </code></pre>
  
  <p>but when I do it in php script it doesn't run. </p>
  
  <pre><code>$val="1234";
  $comm = passthru("C:\abc\prog.exe ".$val)
  </code></pre>
  
  <p>but </p>
  
  <pre><code>$comm = passthru("dir");
  echo $comm; 
  </code></pre>
  
  <p>works fine.</p>
  
  <p>I'm running Windows 7.</p>
  
  <p>P.S I've also tried <code>system()</code> and <code>shell_exec()</code></p>