A self-contained CodeCoverage compatible driver for PHP. When PCOV is left unset, PCOV will attempt to find src, lib or, app in the current working directory, in that order; If none are found the current directory will be used, which may waste resources storing coverage information for the test suite. If PCOV contains test code, it's recommended to set the exclude command to avoid wasting resources. To avoid unnecessary allocation of additional arenas for traces and control flow graphs, PCOV should be set according to the memory required by the test suite. To avoid reallocation of tables, PCOV should be set to a number higher than the number of files that will be loaded during testing, inclusive of test files. interoperability with Xdebug is not possible. At an internal level, the executor function is overridden by PCOV, so any extension or SAPI which does the same will be broken. PCOV is zero cost, code runs at full speed.