day01_14.遍历数组

<?php
    $a = array('a','b','c');
    print_r($a);
?>

　　输出结果:Array ( [0] => a [1] => b [2] => c )

当给一个数组没有分配键的情况下,会自动从0开始分配

<?php
    $arr = array('a','b','c','d');
    $a = 0;
    while($a<=3){
        echo $arr[$a],'<br>';
        $a = $a + 1;
    }
?>

　　

关联数组不能用循环

接下来就引出一个专门循环数组的,foreach

<?php
    foreach ($variable as $key => $value){
        # code...
    }
?>

　　案例

<?php
    $arr2 = array('name'=>'zhangsan','age'=>23,'gender'=>'nv');
    foreach ($arr2 as $key => $value){
        echo $value,'<br>';
    }
?>

输出结果:

zhangsan
23
nv

<?php
    $arr2 = array('name'=>'zhangsan','age'=>23,'gender'=>'nv');
    foreach ($arr2 as $key => $value){
        echo $key,':',$value,'<br>';
    }
?>

输出结果:

name:zhangsan
age:23
gender:nv

<?php
    $arr2 = array('name'=>'zhangsan','age'=>23,'gender'=>'nv');
    foreach ($arr2 as $key){
        echo $key,'<br>';
    }
?>

当as后面只跟一个变量的话,无论你命名这个变量,都是指向值

输出结果:

zhangsan
23
nv

array_keys   返回数组中所有的键名,但是foreach更加好,想要key就有key,想要value就有value

<?php
    $arr2 = array('name'=>'zhangsan','age'=>23,'gender'=>'nv');
    print_r(array_keys($arr2));
?>