05c02-1.php

来自「介绍PHP5的给类型函数应用」· PHP 代码 · 共 90 行

<?php
// A library to implement stacks in PHP via arrays

// The Initialize function creates a new stack:
function &stack_initialize() {
    // In this case, just return a new array
    $new = array();
    return $new;
}

// The destory function will get rid of a stack
function stack_destroy(&$stack) {
    // Since PHP is nice to us, we can just use unset
    unset($stack);
}

// The push operation on a stack adds a new value unto the top of the stack
function stack_push(&$stack, $value) {
    // We are just adding a value to the end of the array, so can use the 
    //  [] PHP Shortcut for this.  It's faster than usin array_push
    $stack[] = $value;
}

// Pop removes the top value from the stack and returns it to you
function stack_pop(&$stack) {
    // Just use array pop:
    return array_pop($stack);
}

// Peek returns a copy of the top value from the stack, leaving it in place
function stack_peek(&$stack) {
    // Return a copy of the value on top of the stack (the end of the array)
    return $stack[count($stack)-1];
}

// Size returns the number of elements in the stack
function stack_size(&$stack) {
    // Just using count will give the proper number:
    return count($stack);
}

// Swap takes the top two values of the stack and switches them
function stack_swap(&$stack) {
    // Calculate the count:
    $n = count($stack);
    
    // Only do anything if count is greater than 1
    if ($n > 1) {
        // Now save a copy of the second to last value
        $second = $stack[$n-2];
        // Place the last value in second to last place:
        $stack[$n-2] = $stack[$n-1];
        // And put the second to last, now in the last place:
        $stack[$n-1] = $second;
    }
}

// Dup takes the top value from the stack, duplicates it, 
//  and adds it back onto the stack
function stack_dup(&$stack) {
    // Actually rather simple, just reinsert the last value:
    $stack[] = $stack[count($stack)-1];
}

// Let's use these to create a small stack of data and manipulate it.
//  Start by adding a few numbers onto it, making it: 73 74 5
$mystack =& stack_initialize();
stack_push($mystack, 73);
stack_push($mystack, 74);
stack_push($mystack, 5);

// Now duplicate the top, giving us:  73 74 5 5
stack_dup($mystack);

// Check the size now, it should be 4
echo '<p>Stack size is: ', stack_size($mystack), '</p>';

// Now pop the top, giving us: 5
echo '<p>Popped off the value: ', stack_pop($mystack), '</p>';

// Next swap the top two values, leaving us with: 73 5 74
stack_swap($mystack);

// Peek at the top element to ensure it is 74
echo '<p>Current top element is: ', stack_peek($mystack), '</p>';

// Now destroy it, we are done.
stack_destroy($mystack);
?>