// Set url
$url = 'http://edition.cnn.com/2015/04/03/politics/white-house-congress-iran-nuclear-deal/index.html';

// This function is going to go to a url or file and pull all the data that's held in it.
$html = file_get_contents($url);

// This function allows user to disable standard libxml errors and enable user error handling if you are so worried about using @ with warnings
libxml_use_internal_errors(true);

// Load the document
$doc = new DomDocument();

// Set array to hold meta name & value
$data = array();

if (!empty($html)) {
    if ($doc->loadHTML($html)) {
        $xpath = new DOMXPath($doc);
        $query = '//*/meta[starts-with(@property, \'og:\')]';
        $metas = $xpath->query($query);

        foreach ($metas as $meta) {

            // Get name
            $property = $meta->getAttribute('property');

            // Get value
            $content = $meta->getAttribute('content');

            // Assign name & value to array
            $data[$property] = $content;
        }
    }
    else {
        foreach (libxml_get_errors() as $error) {
            // handle errors here
        }
    }
}
print_r($data);