test-reverse.php

<?php
function reverse( $arr ) {
        $len = count( $arr );
        for ( $i = 0; $i < $len/2; $i++ ) {
                list( $arr[$i], $arr[$len-$i-1] ) = array( $arr[$len-$i-1], $arr[$i] );
        }
        return $arr;
}
$test = array('a', 'b', 'c', 'd', 'e');
var_dump( reverse( $test ) );