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I would expect that such software is resource expensive (cpu and memory) and therefore i don't expect such software to be availabe... Luckily enough you can use the system (and friends) function to execute external programs.. or write an extension that interfaces with the software...
PHP isn't an optimal language for image processing, especially for intensive operations like facial recognition. As timvw suggests, if you must you PHP, use external or more native (compiled) functionality to perform it.