PHP正则表达式：包含量词的OR语句

Question

Why does an?|the not work? I'm using PHP's preg_match().

Here's the full regex: "/^an?|the (.+?) (is|was) an? (.+?)$/" .

I want it to match "the mona lisa is a painting" and "a dog is an animal" .

It was working fine until I added in the |the to accommodate the first string example.

Thanks!

Answer 1

The way you wrote it it either matches using

^an?

or

the (.+?) (is|was) an? (.+?)$

which is obviously not what you want. You have to put it in parantheses the way you did it with is|was :

/^(an?|the) (.+?) (is|was) an? (.+?)$/

To prevent a group from being included in the result, use a non-matching group which syntax is (?: ) . So just use it like this:

/^(?:an?|the) (.+?) (is|was) an? (.+?)$/