Update PHP colour to reflect php.net

Currently the PHP colour is very similar to C#, and seems to have been pull from thin air. PHP has a perfectly nice distinctive purple, used on [php.net](http://php.net) since forever. This pull request changes PHP's colour to a dark shade of that purple.

Before                                   | After
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![](http://www.colorhexa.com/6e03c1.png) | ![](http://www.colorhexa.com/4f5d95.png)
Merge pull request #1156 from quarterto/patch-1

Update PHP colour to reflect php.net