如何编写reg express以在php中获得以下模式？

Question

There is a website and I would like to get all the <td> (any content) </td> pattern string

So I write like this:

preg_match("/<td>.*</td>/", $web , $matches);
            die(var_dump($matches));

That return null, how to fix the problem? Thanks for helping

Answer 1

OK.

You are only not escaping properly I guess. Also use groups to capture your stuff properly.

<td>(.*)<\/td>

should do. You can try this regex on your given text here . Don't forget the global flag if you are matching ALL td's. ( preg_match_all in PHP)

Usually parsing HTML with regex is not a good idea, try to use DOM parsers instead. Example -> http://simplehtmldom.sourceforge.net/

Test the above regex with

$web = file_get_contents('http://www.w3schools.com/html/html_tables.asp' ); 
preg_match_all("/<td>(.*)<\/td>/", $web , $matches); 
print_r( $matches);

Answer 2

Lazy Quantifier, Different Delimiter

You need .*? rather than .* , otherwise you can overshoot the closing </td> . Also, your / delimiter needed to be escaped when it appeared in </td> . We can replace it with another one that doesn't need escaping.

Do this:

$regex = '~<td>.*?</td>~';
preg_match_all($regex, $web, $matches);
print_r($matches[0]);

Explanation

• The ~ is just an esthetic tweak—you can use any delimiter you like around your regex patttern, and in general ~ is more versatile than / , which needs to be escaped more often, for instance in </td> .
• The star quantifier in .*? is made "lazy" by the ? so that the dot only matches as many characters as needed to allow the next token to match (shortest match). Without the ? , the .* first matches the whole string, then backtracks only as far as needed to allow the next token to match (longest match).