双向循环链表

<?php

class double_link {
    public $name;
    public $next;
    public $prev;

    public function __construct($name) {
        $this->name = $name;
    }
}

function get_double_link($total) {
    $current = $first = new double_link(1);
    $pre = NULL;

    for ($i=2; $i < $total; $i++) { 
        $current -> next = new double_link($i);
        $current -> prev = $pre;
        $pre = $current->next;
        $current = $current->next;
    }
　　
　　
　　 $first -> prev = $current;
    $current->prev = $pre;
    $current->next = $first;

    return $first;
}

var_dump(get_double_link(5));