PHP method for a fast live search from XML file [closed]

Question

I have used this PHP method for a live search from XML file which uses the following functions:

DOMDocument();
getElementsByTagName('');
childNodes.

The XML file is done by me and consists information like this:

<?xml version="1.0"?>
<pages>
    <link>
        <title>A Coruna</title>
        <title2>Spain</title2>
        <url>http://...</url>
    </link>

The file is saved on the same server where the site is saved.

It works fine but it is slow at times. Meaning that even there is only 3000 lines of code in the XML file, it still takes sometimes a few seconds to find the data. Is there another method of making it work faster?

Example of the live search is here: http://time-time.net/time/london-uk.php