Class C Block Range

[Ninjakreborn]

<?php
    echo '<br /><h1>C Class Summary</h1><br />';
    echo '<table><tr><th>Backlink</th><th>IP Address</th></tr>';
    foreach ($unique_backlinks as $v) {
        echo '<tr>';
        echo '<td>'.$v.'</td>';
        echo '<td>'.gethostbyname($v).'</td>';
        echo '</tr>'; 
    }
    echo '</table>';
?>

This prints out all domains with there IP address. Is there a way to expand this to get the IP block range as well. Is there a function in PHP that'll retrieve the block range?