title: Php replacing strings in html ouput
body: <p>I am trying to replace the first string in the code </p>
  
  <pre><code>$confirmation_message = apply_filters("pmpro_confirmation_message",  $confirmation_message, false);
      $confirmation_message = preg_replace('mysite.com', 'mysite.com?true', $str, 1);
      echo $confirmation_message;
  </code></pre>
  
  <p>But it is giving me a weird error </p>
  
  <pre><code>   Delimiter must not be alphanumeric or backslash line
  </code></pre>
  
  <p>Here's the original output of $confirmation_message </p>
  
  <pre><code>   &lt;p&gt;&lt;font&gt;&lt;font class=""&gt;Visit your new site here: &lt;/font&gt;&lt;/font&gt;&lt;a href="mysite.com/"&gt;&lt;font&gt;&lt;font class=""&gt;mysite.com&lt;/font&gt;&lt;/font&gt;&lt;/a&gt;&lt;/p&gt;
  
    &lt;p&gt;&lt;font&gt;&lt;font class=""&gt;Manage your new site here: &lt;/font&gt;&lt;/font&gt;&lt;a href="mysite.com/wp-admin/"&gt;&lt;font&gt;&lt;font class=""&gt;mysite.com/admin&lt;/font&gt;&lt;/font&gt;&lt;/a&gt;&lt;/p&gt;
  </code></pre>