PHP ships with a lot of third party C libraries that are exposed in PHP with usually their original function names. Object orientation came with PHP 4 and later with PHP 5 the new better one (5.3+ with namespace support, traits, etc.).

You can think of PHP as a mixture of C, C++ and Java for web development and CLI tools. I personally use all four languages, each one for specific purposes where the fit best. You can find function names like strstr in C, C++ and PHP (= indexOf in Java and JavaScript) - not a big deal.