How to fix a preg_match bug

This is the second time I try to fix the preg_match bug with a number 50887. The first time I tried it, less than two months ago, my solution was buggy too, and for this reason I have unpublished it.

There are many different scenarios that I didn’t take into account, but almost all of them were related to How to count expected matches of a PHP regular expression. The rest were essentially the same: I thought that the preg_match bug was affecting just the last optional match. Later I found instead that it affects really all the matches at the end, any number of them, be they optional or not. Due to this little misunderstanding I had to rewrite a big portion of the function.

{[ .fix | 1.hilite(=php=) ]}

For the function ando_preg_count_groups(…) see the post How to count expected matches of a PHP regular expression.

Minimal Tests

Test 1a

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Test 1b

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Test 1c

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The following tests are based on $regex = ‘(?|Saturday|Sun(day)?)’;.

Test 2a

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Test 2b

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Test 2c

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The following tests are based on $regex = ‘(?|(Sat)ur(day)|Sun(day)?)’;.

Test 3a