title: sed doesn't work with PHP exec function
body: <pre><code>echo "sed -i 's/NULL/\\N/g' ".$_REQUEST['para'].".sql";
  </code></pre>
  
  <p>The above statement works. But it fail when I use it in exec like this...</p>
  
  <pre><code>exec("sed -i 's/NULL//\/\/\N/g' ".$_REQUEST['para'].".sql");
  </code></pre>