How to get the position of a Regex match in a string? [duplicate]

Question

I know how to use preg_match and preg_match_all to find the actual matches of regex patterns in a given string, but the function that I am writing not only needs the text of the matches, but to be able to traverse the string AROUND the matches...

Therefore, I need to know the position of the match in the string, based on a regex pattern.

I can't seem to find a function similar to strpos() that allows regex...any ideas?

Answer 1

You can use the flag PREG_OFFSET_CAPTURE for that:

preg_match('/bar/', 'Foobar', $matches, PREG_OFFSET_CAPTURE); var_export($matches); 

Result is:

array (   0 =>    array (     0 => 'bar',     1 => 3,     // <-- the string offset of the match   ), ) 

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In a previous version, this answer included a capture group in the regular expression (preg_match('/(bar)/', ...)). As evident in the first few comments, this was confusing to some and has since been edited out by @Mikkel. Please ignore these comments.

Answer 2

preg_match has an optional flag, PREG_OFFSET_CAPTURE, that records the string position of the match's occurence in the original 'haystack'. See the 'flags' section: http://php.net/preg_match