title: php search a string for 4 or more numbers with a decimal and format it to currency
body: <p>I have an include that I'm pulling into a php page that's just a standard table with prices and whatnot.</p>
  
  <p>E.g. </p>
  
  <pre><code>    &lt;table&gt;
    &lt;tr&gt;
      &lt;td&gt;90&lt;/td&gt;
      &lt;td&gt;&amp;nbsp;&lt;/td&gt;
      &lt;td&gt;&amp;nbsp;&lt;/td&gt;
      &lt;td&gt;&amp;nbsp;&lt;/td&gt;
      &lt;td&gt;&amp;nbsp;&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;Hard Top&lt;/td&gt;
      &lt;td&gt;17170.00&lt;/td&gt;
      &lt;td&gt;5930.00&lt;/td&gt;
      &lt;td&gt;20818.00&lt;/td&gt;
      &lt;td&gt;2282.00&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;Hard Top XS&lt;/td&gt;
      &lt;td&gt;20972.50&lt;/td&gt;
      &lt;td&gt;7197.50&lt;/td&gt;
      &lt;td&gt;25381.00&lt;/td&gt;
      &lt;td&gt;2789.00&lt;/td&gt;
    &lt;/tr&gt;
  &lt;/table&gt;
  </code></pre>
  
  <p>What I need to do is search through the include (I presume by putting it into a string first) then formatting all the numbers that are >= 4 characters long with a decimal point into currency.</p>
  
  <p>so i would format '17170.00' as '£17,170.00' but I want to leave '90' alone as that's a title.</p>
  
  <p>I know how to format into currency, that part's easy. But how do I search for clusters of numbers in a string that are >= 4 characters and have a decimal in the middle of them?</p>
  
  <p>Would it use a regex (I've used them before but the intricacies still elude me) or would it be something simpler?</p>