php - Get content from html file

I have a list of html files. Each file repeatedly has the strings onClick="rpd(SOME_NUMBER)" . I know how to get the content from the html files, what I would want to do is get a list of the "SOME_NUMBER" . I saw that I might need to do a preg_match, but I'm horrible at regular expressions. I tried

$file_content = file_get_contents($url);    
$pattern= 'onClick="rpd(#);"';
preg_match($pattern, $file_content);

As you could imagine... it didn't work. What would be the best way to get this done? Thanks!

Answer

This should get it done:

    $file_content ='234=fdf donClick="rpd(5);"as23 f2 onClick="rpd(7);" dff fonClick="rpd(8);"';    
    $pattern= '/onClick="rpd\((\d+)\);"/';

    preg_match_all($pattern, $file_content,$matches);
    var_dump( $matches);

The output is like this:

    array (size=2)
    0 => 
    array (size=3)
      0 => string 'onClick="rpd(5);"' (length=17)

      1 => string 'onClick="rpd(7);"' (length=17)
      2 => string 'onClick="rpd(8);"' (length=17)
    1 => 
    array (size=3)
      0 => string '5' (length=1)
      1 => string '7' (length=1)
      2 => string '8' (length=1)