title: Extract data PHP string
body: <p>I have used file_get_contents() to basically get the source code of a site into a single string variable.</p>
  
  <p>The source contains many rows that looks like this:
  <code>&lt;td align="center"&gt;&lt;a href="somewebsite.com/something"&gt;12345&lt;/a&gt;&lt;/td&gt;</code></p>
  
  <p>(and a lot of rows that don't look like that). I want to extract all the idnumbers (12345 above) and put them in an array. How can I do that? I assume I want to use some kind of regular expressions and then use the preg_match_all() function, but I'm not sure how...</p>