explode和preg_match比较

<?php
    $starttime = explode(" ",microtime());
    $a="/tmp/trunk/trunk/app/controllers/Abstract.php - Unexpected token: class, line: 3, col: 14, file: /tmp/trunk/trunk/app/controllers/Abstract.php.";
    // $b=explode(":", explode("-", $a)[1])[0];

    preg_match("/(\\w+ \\w+):/", $a, $b);

    $endtime = explode(" ",microtime());
    $thistime = $endtime[0]+$endtime[1]-($starttime[0]+$starttime[1]);
    echo $thistime;