regex＆align：％HORIZONTAL％|％VERTICAL％

Question

I would like to have a regex that matches something like this:

&align:%HORIZONTAL%|%VERTICAL%

%HORIZONTAL% may be "left" or "right" or "center"

%VERTICAL% may be "top" or "bottom" or "center"

I tried something like this:

&align:(left|right|center)\|(top|bottom|center)

And I got this:

Array(
[0] => &align:left|center
[1] => left
[2] => top
)

What would I have to change to get only one match at all? The [1] and [2] must not be possible.

Answer 1

Parentheses serve two purposes — grouping and capturing. To get the grouping you want without capturing the matches, use ?: :

&align:(?:left|right|center)\|(?:top|bottom|center)

Manual reference: http://uk3.php.net/manual/en/regexp.reference.subpatterns.php