Regular expression hash match

Question

The regex below takes the number (company id) out from the URL below, but I'm trying to find out how it works. What does hash to and pluses do?

preg_match('#/company/([0-9]+)/(.+)#',http://test.net.au/company/198/test,$m);

the `#` here is regexp boundaries, the `+` is the any number of character before `+` (>=1) — zb', Nov 22 '12 at 00:49
* See also [Open source RegexBuddy alternatives](http://stackoverflow.com/questions/89718/is-there) and [Online regex testing](http://stackoverflow.com/questions/32282/regex-testing) for some helpful tools, or [RegExp.info](http://regular-expressions.info/) for a nicer tutorial. And the PHP manual explains quite a bit too: http://php.net/manual/en/reference.pcre.pattern.syntax.php — mario, Nov 22 '12 at 00:49

score 1 · Answer 1 · answered Nov 22 '12 at 00:49

Hash here is a regular expression delimiter. You can use almost anything as a delimiter, like ~, !, etc.

+ is a quantifier that means repetition from 1 to infinity.

[0-9]+ --- 1 or more numbers in a row
.+     --- any character one or more times in a row

score 1 · Answer 2 · answered Nov 22 '12 at 00:49

The first and last characters in the regex are delimiters. They are there just to say here is where the regex starts and here is where it stops:

Usually / is used:

Example: "/foo/";
         "#bar#";

In your example you are trying to match "/company/" so the delimiter can't be a / so # is used instead.

The plus + means match 1 or more of the previous entry. Meaning in your case it will match one or more digits (From 0 to 9)

score 1 · Answer 3 · answered Nov 22 '12 at 00:51

The hashes are just used as the regex pattern's bounding delimiters. Commonly developers use /, ~, or # for this. In this case # was used to prevent the need to escape the /'s in the regex pattern.

The + indicates that there must be one or more of the preceding element, which in the first case is actually a character class specifying all digits. In the second case it just means there need to be one or more of any character (. is wildcard).

Regular expression hash match

3 Answers3