如何在PHP中捕获与可选空格的链接？ [重复]

Question

This question already has an answer here:

• How do you parse and process HTML/XML in PHP? 30 answers

From a file_get_contents I get the HTML code of a url.

$html = file_get_contents($url);

Now I would like to capture the href link.

The HTML code is:

<li class="four-column mosaicElement">
<a href="https://example.com" title="Lorem ipsum">
...
</a>
</li>
<li class="four-column mosaicElement">
<a href="https://example.org" title="Lorem ipsum">
...
</a>
</li>

So I'm using this:

preg_match_all('/class=\"four-column mosaicElement\"><a href=\"(.+?)\" title=\"(.+?)"/m', $html, $urls, PREG_SET_ORDER, 0);

foreach ($urls as $key => $url) {
    echo $url[1];
}

How do I solve this problem?

</div>

Answer 1

Here, we can also use an expression with positive lookahead and optional spaces, just in case,

(?=class="four-column mosaicElement")[\s\S]*?href="\s*(https?[^\s]+)\s*"

and our desired URLs are in this group:

(https?[^\s]+)

DEMO

TEST

$re = '/(?=class="four-column mosaicElement")[\s\S]*?href="\s*(https?[^\s]+)\s*"/m';
$str = '<li class="four-column mosaicElement">
<a href="https://example.com" title="Lorem ipsum">
...
</a>
</li>
<li class="four-column mosaicElement">
<a href="https://example.org" title="Lorem ipsum">

<li class="four-column mosaicElement">
<a href="   https://example.org   " title="Lorem ipsum">

<li class="four-column mosaicElement">
<a href="   https://example.org                " title="Lorem ipsum">
...
</a>
</li>
';

preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);

foreach ($matches as $key => $url) {
    echo $url[1] . "
";
}

Output

https://example.com
https://example.org
https://example.org
https://example.org

RegEx Circuit

jex.im visualizes regular expressions: