PHP - preg_match() result in 0 matching values - php

Question

I was trying to do web scraping for my personal webpage, using the bio and pics from a website profile (http://about.me/fernandocaldas) so whenever I change that profile the content in my web bio will also do.
The desired values are between
<script type="text/json" class="json user" data-scope="view_profile" data-lowercase_user_name="fernandocaldas">
and
</script>
Here is my code:
$thtml = file_get_contents('http://about.me/fernandocaldas');
$matchval = '/\<script type=\"text\/json\" class=\"json.*?>(.*?)\<\/script\>/i';
preg_match($matchval, $thtml, $match);
var_dump($match);
if($match){
echo "match!\n";
foreach($match[1] as $val)
{
echo $val."<br>";
}
}
But the result is always array(0) {} for the var_dump.

Answer 1

Regular expressions are never a good idea for HTML: today regex seems to work, but tomorrow they will fail!1
Frequently programmers think: “why I have to init a parser, load the HTML, performs a lot of queries if I can do it with only one line of regex code?”. The answer is “why choose the road that leads you in the wrong direction, although shorter?”.
In your case by using a Parser you can also shorten your code.
First, load your HTML page, init a new DOMDocument object, load HTML string into it and init a DOMXPath object (DOMXPath permits to perform complex HTML queries):
$dom = new DOMDocument();
libxml_use_internal_errors(1);
$dom->loadHTML( $html );
$xpath = new DOMXPath( $dom );
Search for the element(s) with tag <script> and class “json user”:
$found = $xpath->query( '//script[#class="json user"]' );
if( !$found->length ) die( 'Error retrieving JSON' );
Put the node value of first (and unique, in your page) node in a variable (I also trim it, but it is unnecessary) and decode it with json_decode():
$json = trim( $found->item(0)->nodeValue );
$user = json_decode( $json );
Now, in $user object, you have all the data you need. In $user->first_name you have your first name, in $user->bio you have your biography. By a print_r( $user ) you can display the complete $user structure to see how to access to each element.
Read more about DOMDocument
Read more about DOMXPath
Read why you can't parse [X]HTML with regular expressions
1 If the HTML structure change, also a parser will fail.