07c10-1.php

介绍PHP5的给类型函数应用

<?php
// Define a class to implement linked lists, a linked list node.
class Linked_List_Node {
    // Define the variable to hold our data:
    public $data;
    // And a variable to hold the next object in the chain:
    public $next;
    
    // A constructor method that allows for data to be passed in
    public function __construct($d = NULL) {
        $this->data = $d;
    }
    
    // Now create some methods that will make handling lists more automatic:

    // First of all a method that will insert a Node after this one
    public function insertAfter(Linked_List_Node $insert) {
        // This assumes a single node will be passed in not an entire list.
        // If you pass a node from a list the rest of the list will be lost.

        // Set the new node's next, to be this node's next.
        $insert->next = $this->next;

        // Now set this node's next, to the new node:
        $this->next = $insert;
    }

    // Now a method that will remove the node after this one:
    public function removeAfter() {
        // Store a reference to the node in question:
        $ref = $this->next;
        
        // Now jump over this node, linking to its child (if it existed)
        if (isset($this->next->next)) {
            $this->next = $this->next->next;
        } else {
            // Otherwise just make it null
            $this->next = NULL;
        }
        
        // Now, destroy the original object:
        unset($ref);
    }

    // Now also define a method that will output an entire linked
    //  list, starting from this node.
    public function asString() {
        // If another child exists, then retrieve its value:
        $children = '';
        if ($this->next) {
            $children = ', ' . $this->next->asString();
        }

        // Return this data, concatenated with that of all it's children:
        return $this->data . $children;
    }
}

// Create a new linked list:
$list = new Linked_List_Node('PHP');

// Now add an element after that one:
$list->insertAfter(new Linked_List_Node('Perl'));

// And then insert one in between the two:
$list->insertAfter(new Linked_List_Node('Javascript'));

// Echo this out as a string:  PHP, Javascript, Perl
echo '<p>', $list->asString(), '</p>';

// Now remove the last element:
$list->next->removeAfter();

// And output the string again: PHP, Javascript
echo '<p>', $list->asString(), '</p>';
?>