regex

What is the difference between a plus and a star in regex?

What is the difference between:

(.+?)

and

(.*?)

when I use it in my PHP preg_match regex?

Solution

  • They are called quantifiers.

    * 0 or more of the preceding expression

    + 1 or more of the preceding expression

    Per default a quantifier is greedy, that means it matches as many characters as possible.

    The ? after a quantifier changes the behaviour to make this quantifier "ungreedy", means it will match as little as possible.

    Example greedy/ungreedy

    For example on the string "abab"

    a.*b will match "abab" (preg_match_all will return one match, the "abab")

    while a.*?b will match only the starting "ab" (preg_match_all will return two matches, "ab")

    You can test your regexes online e.g. on Regexr, see the greedy example here