title: preg_match: ensure the start and the end contains something
body: <p>I want to have the regular expression that makes sure the beginning of the string contains 'http://' and '/' and the end.</p>
  
  <p>This is a longer version I came up with,</p>
  
  <pre><code>if(!preg_match("/(^http:\/\//", $site_http)) 
  {
   $error = true;
   echo '&lt;error elementid="site_http" message="site_http - Your link appears to be invalid. Please confirm that your link contains http:// at the start."/&gt;';
  }
  elseif (!preg_match("/\/$/", $site_http)) 
  {
   $error = true;
   echo '&lt;error elementid="site_http" message="site_http - Your link appears to be invalid. Please confirm that your link has ended with a /."/&gt;';
  }
  </code></pre>
  
  <p>but I thought these two expressions can put together like below, but it wont work,</p>
  
  <pre><code>if(!preg_match("/(^http:\/\/)&amp;(\/$)/", $site_http)) 
  {
   $error = true;
   echo '&lt;error elementid="site_http" message="site_http - Your link appears to be invalid. Please confirm that your link contains http:// at the start and a / at the end."/&gt;';
  }
  </code></pre>
  
  <p>the multiple expressions that I try to combine must be wrong! any idea?</p>
  
  <p>thanks,
  Lau</p>