Why is this regex throwing a 'PREG_BACKTRACK_LIMIT_ERROR' error?

Question

In the example at PHP.net, it says that the regular expression /(?:\D+|<\d+>)*[!?]/ matched against foobar foobar foobar throws a PREG_BACKTRACK_LIMIT_ERROR error. Can anybody explain why?

score 5 · Answer 1 · answered Sep 11 '12 at 18:05

5

Catastrophic Backtracking.

Incorrect nesting.

answered Sep 11 '12 at 18:05

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Thanks. That is a good link. Can you tell me what is meant by the sentence **The group has one iteration it can backtrack into.** in the 2nd line of the 3rd paragraph? – SexyBeast Sep 11 '12 at 19:02

Why is this regex throwing a 'PREG_BACKTRACK_LIMIT_ERROR' error?

1 Answers1

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