title: Replace exact variable string with variable text in PHP?
body: <p>I'm working on a replying system similar to twitters.<br>
  In a string there is a piece of text where the id is variable ex.: <code>14&amp;</code> , <code>138&amp;</code> depending to who you're replying.<br>
  How can I find the <code>14&amp;</code> in a string and replace it with <code>&lt;u&gt;14&amp;&lt;/u&gt;</code>?  </p>
  
  <p>This is how it looks:  </p>
  
  <pre><code>14&amp; this is a reply to the comment with id 14
  </code></pre>
  
  <p>This is how it should look like:</p>
  
  <pre><code>&lt;u&gt;14&amp;&lt;/u&gt; this is a reply to the comment with id 14
  </code></pre>
  
  <p>How can I do this in PHP? Thanks in advance!</p>