php - simple regex pattern confusion -


somebody give me hand please. why getting below output

$pattern = "#([a-z])*|(chol)#"; preg_match($pattern, 'chol',$m);  print_r($m) // array                 (                   [0]=> 'chol',                   [1]=> 'l'                 )

why first sub capture matched l character while full match chol. may missing something. expected output below

array         (          [0]=> 'chol',          [1]=> 'chol'         )

i don't think pattern overly complicated confuse me.

you quantified group. need quantify [a-z] character class.

use

$pattern = "#([a-z]*)|(chol)#";

see php demo , more details @ repeating capturing group vs. capturing repeated group. in short: ([a-z]*) match , capture 0 or more lowercase ascii letters group 1 , contain whole chunk of these letters, while ([a-z])* match , capture 0 or more occurrences of consequent lowercase ascii letter, while overwriting each previous occurrence new one.

you might consider removing redundant capturing groups if not using them.

more, since unanchored alternation, note [a-z]* match chol , second alternative never match. might consider putting (chol) first alternative more specific.

so, suggest

$pattern = "#(chol)|([a-z]*)#";

more on @ remember regex engine eager.


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