preg_match_all doesn't match when using a carat (^)

问题

I'm using preg_match_all to find a URL in a HTML file. The URL always appears at the start of the line, with no leading space, like this:

<A HREF="/link/to/here"><strong>Next</strong></A>

I used this to match it:

preg_match_all('|^<A HREF="(?<url>.*?)"><strong>Next</strong>|', $html, $url_matches);

It didn't work until I removed the carat (^) character. I thought that the carat matched the start of a line. Why is it causing my match to fail?

回答1:

You have to add the m modifier:

preg_match_all('|^<A HREF="(?<url>.*?)"><strong>Next</strong>|m', $html, $url_matches);

then ^ matches at start of a line, else it would only match at the start of the entire string.

More Info: http://php.net/manual/en/reference.pcre.pattern.modifiers.php

回答2:

^ matches start-of-string not start-of-line. Use the m ("multi-line") modifier: //m

来源：https://stackoverflow.com/questions/6179991/preg-match-all-doesnt-match-when-using-a-carat