split array if previous element is not same

split_sorted.php

function split_sorted()
{
        $arr = array('1','2','2','3');
        $output = array();

        $previous = null;
        $temp = array();
        foreach($arr as $row){
            if(isset($previous) === true and $previous !== $row){
                $output[] = $temp;
                $temp = array();
            }
            $temp[] = $row;
            $previous = $row;
        }
        $output[] = $temp;
        echo"<pre>";
        print_r($output);
        echo"</pre>";
}