title: PHP: preg_match issue
body: <p>I'm having an issue with preg_match, somehow, I'm still new with preg_match and I still can't get it working like what I want.</p>
  
  <p>Here's my data...</p>
  
  <p>String_Length_Location_Time_Degree_Alt</p>
  
  <p>I'm using this preg_match to split up the data into the varibles...</p>
  
  <pre><code>preg_match('(?&lt;data1&gt;)_(?&lt;data2&gt;)_(?&lt;data3&gt;)_(?&lt;data4&gt;)_(?&lt;data5&gt;)_(?&lt;data6&gt;)', $str, $matches);
  </code></pre>
  
  <p>And I get the following error "preg_match(): Unknown modifier '_' in <b>[...][...]</b>"</p>
  
  <p>Does anyone have an idea what can be the issue?</p>
  
  <p>Thanks!</p>