I started my web programming using ASP but after a while decided to give PHP a go. A couple of examples spring to mind.
A simple page which allowed users in one of our departments to view daily comments from a log. One day I had a complaint that the page took 15 seconds to load in the browser. Repeated tests on that day's data gave the same result. The comments on this day were particularly verbose. I wrote a PHP version which, when tested on that same day's data, repeatedly produced the results in just over 0.2 seconds (70x faster). This was an exception but, normally, PHP was better that 3x faster.
A page which allowed the public to enter their location and a search radius and it would find the time of all bus services, in the next hour, which departed from stops in the search radius. There was, however, a problem in the city centre with a high stop density. A radius of 200m would cause the whole thing to timeout after 30 seconds. Again a PHP rewrite was tried. Even at a radius of 2000m it displayed all the stops and times within a few seconds - no timing out.
Score 2 for PHP. After those my boss stopped objecting to my using PHP. (His objection had been on the grounds that it wasn't a MS product!)