title: What is the meaning of \x00 , \x04 in PHP
body: <p>i have some codes having the <strong>\x00</strong> and <strong>\x04</strong> <strong><em>hex codes</em></strong>, what does it means?</p>
  
  <pre><code>$str= implode("\x00", $var['message']); //line 1
  $id= $var['message'] . "\x04" . $id;    //line 2
  </code></pre>
  
  <p>what will happen in the <strong>line1 and line2</strong> I want to write these into a external file as <strong>binary format</strong>.</p>
  
  <p>where do i get all information like this.</p>