title: equivalence of contentPlaceHolder in php
body: <p>I am using PHP and CodeIgniter. In every view file, I include the <code>header.php</code>, seen below:</p>
  
  <pre><code>&lt;head&gt;
    &lt;link rel="..."&gt;
    &lt;script type="text/javascript"&gt;...&lt;/script&gt;
  &lt;/head&gt;
  </code></pre>
  
  <p>Notice that the head tag is closed in this file. Now I want to add a <code>&lt;script&gt;</code> tag in another file without modifying <code>header.php</code>. C# has <code>ContentPlaceHolder</code> that can be used to indicate where tags can be added within head tag. Is there any equivalent in php? If not, How can I achieve this?</p>