I have spent an hour today debugging a weird issue: PHPUnit complained that it tried to call an undefined function PHPUnit\Framework\Assert\assertEquals(). Because right now I am working with custom PHP extensions, I suspected that my code somehow corrupted PHP’s internal data structures. But reality prepared me a surprise.
When testing your own PHP extensions, it is very important not to miss any memory leaks. Wherever Valgrind shows a memory leak, you need to check your code for bugs. However, sometimes you can find a memory leak in the PHP Core.