<?php


    $startRaw = '2013-05-10 12:04:58';
    $start = DateTime::createFromFormat('Y-m-d H:i:s', $startRaw );
    
    $endRaw = date("2015-05-10 12:04:58");
    $end = DateTime::createFromFormat('Y-m-d H:i:s', $endRaw );
    
    $diff = $start->diff($end);
    
    echo 'Difference: ' . $diff->format('%y years') . "\n";