Random guess: There will be some difference in the regex engine speed, because PCRE is very fast in common cases. But doing a single regex match is not that m

Random guess: There will be some difference in the regex engine speed, because PCRE is very fast in common cases. But doing a single regex match is not that much work, so it probably boils down to I/O. And PHP might use extra buffering to get better throughput for the common "stream a file" scenario. Similar question with Python being faster than C++: https://stackoverflow.com/questions/9371238/why-is-reading-lines-from-stdin-much-slower-in-c-than-python https://stackoverflow.com/questions/9371238/why-is-reading-l...