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('a','b','c'); 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[] = 'a'; $arr[] = 'b'; $arr[] = 'c'; 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=>'jack',2=>'lucy',500=>'hcoder'); 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] = 'jack'; $arr[2] = 'lucy'; $arr[500] = 'hcoder'; 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('name'=>'张三', 'age'=>18); echo $arr['age']; //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['name'] = '张三'; $arr['age'] = 18; echo $arr['age']; //输出18
简而言之 就是用 $a[] 和 $a=array()

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