PHP regex fails, succeeds on Regex 101

Question

Stumped by this one O_o...

if(preg_match("(\d{1,2})\:(\d{2})", "5:00", $matches) == 1) echo "works";
else echo "don't work";

Will echo

don't work

But the same regex on Regex 101 seems to work fine: http://regex101.com/r/mW1dN9

Do I need a global flag or something?

(1) enable error reporting.... (2) well, I guess that solved itself (you forgot delimiters). — Wrikken, Mar 06 '13 at 17:12
Why does the regex need the delimiters? Why does it fail without them? — parker.sikand, Mar 06 '13 at 17:16

score 3 · Answer 1 · answered Mar 06 '13 at 17:12

3

Your regex pattern needs some delimiters.

if(preg_match("#(\d{1,2})\:(\d{2})#", "5:00", $matches) == 1) echo "works";
else echo "don't work";

answered Mar 06 '13 at 17:12

Peter O'Callaghan

cool that worked. Why exactly are the delimiters necessary? – parker.sikand Mar 06 '13 at 17:13
If you need to use any flags (e.g., global, case-insensitive, etc.), the delimiters show the regexp engine where to find them in the string. They have to be there, even if you're not using flags. – Xophmeister Mar 06 '13 at 17:15
They separate the pattern from the flags. If you were to place an i after the closing delimter, it would make the pattern case insensitive. http://php.net/manual/en/regexp.reference.delimiters.php – Peter O'Callaghan Mar 06 '13 at 17:16
so it sounds like a case of "that's just how it works"? – parker.sikand Mar 06 '13 at 17:17

score 2 · Answer 2 · answered Mar 06 '13 at 17:13

2

You need to put your regular expression within delimiters:

if(preg_match("/(\d{1,2}):(\d{2})/", "5:00", $matches) == 1) echo "works";
else echo "don't work";

Also, you don't need to escape the :, but it works either way.

answered Mar 06 '13 at 17:13

Xophmeister

2 Answers2