PHP : Web Automation - [11.9] Extracting Links from an HTML File

11.9.1 Problem

You need to extract the URLs that are specified inside an HTML document.

11.9.2 Solution

Use the pc_link_extractor( ) function shown in Example 11-2.

Example 11-2. pc_link_extractor( )

function pc_link_extractor($s) {
  $a = array();
  if (preg_match_all('/<a\s+.*?href=[\"\']?([^\"\' >]*)[\"\']?[^>]*>(.*?)<\/a>/i',
                     $s,$matches,PREG_SET_ORDER)) {
    foreach($matches as $match) {
      array_push($a,array($match[1],$match[2]));
    }
  }
  return $a;
}

For example:

$links = pc_link_extractor($page);

11.9.3 Discussion

The pc_link_extractor( ) function returns an array. Each element of that array is itself a two-element array. The first element is the target of the link, and the second element is the text that is linked. For example:

$links=<<<END
Click <a href="http://www.oreilly.com">here</a> to visit a computer book 
publisher. Click <a href="http://www.sklar.com">over here</a> to visit 
a computer book author.
END;

$a = pc_link_extractor($links);
print_r($a);
Array
(
    [0] => Array
        (
            [0] => http://www.oreilly.com
            [1] => here
        )
    [1] => Array
        (
            [0] => http://www.sklar.com
            [1] => over here
        )
)

The regular expression in pc_link_extractor( ) won't work on all links, such as those that are constructed with JavaScript or some hexadecimal escapes, but it should function on the majority of reasonably well-formed HTML.