php: preg_match is not greedy?

Asked Jan 10 '17 at 20:29

Active Jan 10 '17 at 20:29

Viewed 19 times

In php, I have the following situation:

$Text = "eb 6; 1 cor 4";
$Regex1 = '((eb 6(; 1)?|1 cor 4)(; )?)+';
$Regex2 = '((eb 6|1 cor 4)(; )?)+';

$Match1 = preg_match("/$Regex1/", $Text, $ArrayMatches1); 
$Match2 = preg_match("/$Regex2/", $Text, $ArrayMatches2);

$Regex2 matches the whole variable: eb 6; 1 cor 4

$Regex1 ends matching eb 6; 1.

Now, PCRE's are supposed to be greedy; since $Regex2 is equivalent to $Regex1 with (; 1) used 0 times, I'd expect $Regex1 to return the longest possible match, while it doesn't happen: it seems that the quantifiers are greedy, but the whole pcre isn't greedy.

Am I missing something or is this a php bug?

asked Jan 10 '17 at 20:29

Paolo Benvenuto

did you try it with the x modifier? – bassxzero Jan 10 '17 at 20:34
Do you ask for an explanation of the two regex difference? – Wiktor Stribiżew Jan 10 '17 at 20:35
the x modifier doesn't solve. – Paolo Benvenuto Jan 10 '17 at 20:37
Note that `(; )?` is not the same as `(; 1)?`. If you use `$Regex1 = '((eb 6(; )?|1 cor 4)(; )?)+';`, see https://regex101.com/r/CaU2lm/3, it will behave as the second regex. – Wiktor Stribiżew Jan 10 '17 at 20:38
I'm not trying to build a pcre that matches the whole variable, I'm trying to understand why I don't get the whole variable with $Regex1 too, in the assumptions that pcre's are greedy – Paolo Benvenuto Jan 10 '17 at 20:40
1

You are mistaken, PCRE cannot be "greedy" or not, only quantifiers can be greedy or lazy. And you just made a typo in the first regex, that is all. – Wiktor Stribiżew Jan 10 '17 at 20:41
So, was that `1` a typo? Or what was your intention? – Wiktor Stribiżew Jan 10 '17 at 20:45
no it wasn't a typo, I was trying to understand why I don't get the whole variable with $Regex1 too, in the assumptions that pcre's are greedy, but you have answered me: "PCRE cannot be "greedy" or not, only quantifiers can be greedy or lazy". Thank you – Paolo Benvenuto Jan 10 '17 at 20:46

php: preg_match is not greedy?

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