It's a black unfilled square with slightly rounded corners. The radii of the rounded corners is very small. In the center of the square there are the letters "PHP" in upper case.
This is a PHP Filled icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,700 icons, all in the same style and quality.