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php如何构造数组

Jun 06, 2016 pm 08:10 PM
php

php如何构造数组

php如何构造数组?php创建数组的几种方法

第1种格式

$数组名称 = array(‘值’, ‘值’, ‘值’,……);

此种格式没有指定数组内元素的键,PHP 会自动以数字的形式创建键,从 0 开始,依次累加。
调用数组的格式 : $数组名称[数字型键]

<?php 
$arr = array(&#39;a&#39;,&#39;b&#39;,&#39;c&#39;); 
echo $arr[1]; 
//输出

第2种格式

$数组名称[] = ‘值’;
$数组名称[] = ‘值’;
$数组名称[] = ‘值’;
……

此种格式同样没有指定数组内元素的键, PHP会自动以数字的形式创建键, 从 0开始,依次累加。
调用数组的格式 : $数组名称[数字型键];

<?php 
$arr[] = &#39;a&#39;; 
$arr[] = &#39;b&#39;; 
$arr[] = &#39;c&#39;; 
echo $arr[1]; 
//输出b

第3种格式
$数组名称 = array(数字类型的键=> ‘值’, 数字类型的键 => ‘值’, 数字类型的键=> ‘值’,……);
调用格式 : $数组名称[数字类型的键];

<?php 
$arr = array(1=>&#39;jack&#39;,2=>&#39;lucy&#39;,500=>&#39;hcoder&#39;); 
echo $arr[500]; 
//输出hcoder

此种格式采用整数作为数组的键,php 对数组的支持非常灵活,可以任意定义数组内的数字。

如果数组内出现了重复的键则最后出现的元素会覆盖前面的所有键,最后一个为有效值。
第4种格式

$数组名称[整数类型键] = ‘值’;
$数组名称[整数类型键] = ‘值’;
$数组名称[整数类型键] = ‘值’;
……

调用格式 : $数组名称[整数类型键];

<?php 
$arr[1] = &#39;jack&#39;; 
$arr[2] = &#39;lucy&#39;; 
$arr[500] = &#39;hcoder&#39;; 
echo $arr[500]; 
//输出hcoder

第5种格式(关联数组)
$数组名称=array(‘字符串形式的键’=>’值’,‘字符串形式的键’=>’值’,……);
调用格式 : $数组名称[‘字符串形式的键’];

<?php 
$arr = array(&#39;name&#39;=>&#39;张三&#39;, &#39;age&#39;=>18);
echo $arr[&#39;age&#39;]; 
//输出18

第6种格式(关联数组)

$数组名称[ ‘字符串形式的键’]=>’值’;
$数组名称[ ‘字符串形式的键’]=>’值’;
……

调用格式 : $数组名称[‘字符串形式的键’];

<?php 
$arr[&#39;name&#39;] = &#39;张三&#39;; 
$arr[&#39;age&#39;] = 18; 
echo $arr[&#39;age&#39;]; 
//输出18

简而言之 就是用 $a[]  和 $a=array()

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