Tips on using each and list functions in PHP

This article mainly introduces the usage skills of each and list functions in PHP. Interested friends can refer to it. I hope it will be helpful to everyone.

1. Usage of each

Let’s look at the API first

array each (array &$array)

This is described in the api: each - returns the current key/value pair in the array and moves the array pointer forward one step

Let's first take a look at what the returned array looks like Like?

<?php 
$arr = array(&#39;你&#39;,&#39;若&#39;,&#39;安&#39;,&#39;好&#39;,&#39;便&#39;,&#39;是&#39;,&#39;晴&#39;,&#39;天&#39;);
print_r(each($arr));
print_r(each($arr));
echo &#39;<hr />&#39;;
/*
返回
Array
(
  [1] => 你
  [value] => 你
  [0] => 0
  [key] => 0
)
Array
(
  [1] => 若
  [value] => 若
  [0] => 1
  [key] => 1
)
*/
//执行相同的一段代码，从‘你&#39;到‘若&#39;，说明each是会每执行一次，游标向数组尾部移动一步
//0和Key存放的是键
//1和value存放的是值
//因此each满足遍历数组的，得到当前的键和值，以及每执行一次，向尾部移动一步游标
//因此循环数组也可以用each这么写
reset($arr);
for(;$tmp=each($arr);){
  echo $tmp[0],&#39;~&#39;,$tmp[1],&#39;<br />&#39;;
}
/*
返回
0~你
1~若
2~安
3~好
4~便
5~是
6~晴
7~天
*/
?>

2. How to use list

Let’s first look at what the api says

Like array(), this Not really functions, but language constructs. list() uses one step to assign values ​​to a set of variables.

Let’s look at an example:

<?php 
list($a,$b)=array(10,20);
echo $a,&#39;~&#39;,$b,&#39;<br />&#39;;
//返回10~20
?>

Yes, you can assign values ​​to a set of variables

Let’s look at another example:

<?php 
list($a,$b,,$c)=array(2=>10,3=>20,4=>30,1=>40);
echo $a,&#39;~&#39;,$b,&#39;~&#39;,$c,&#39;<br />&#39;;
//返回notice~40~20
//执行到$a的时候返回给我一个notice：说数组没有0键
?>

According to the general idea, it should Will return: 10~20~40

Why will this notice~40~20 be returned?

Answer: This involves the operating mechanism of the list. This is how the list is assigned

First of all: ignore the array on the right and look at the variables in the List. From left to right it should be $a = arr[0] $b=arr[1] $c=arr[3]

Then: start assigning values ​​from right to left, the order of assignment is $c=arr[3] $b=arr[1 ] $a=arr[0]

So $c=20 $b = 40 Because there is no arr[0], $a gave a warning

3 .Use each and list to implement array traversal

<?php 
$arr = array(&#39;你&#39;,&#39;若&#39;,&#39;安&#39;,&#39;好&#39;,&#39;便&#39;,&#39;是&#39;,&#39;晴&#39;,&#39;天&#39;);
for(;list($k,$v)=each($arr);){
  echo $k,&#39;~&#39;,$v,&#39;<br />&#39;;
}
/*
return:
0~你
1~若
2~安
3~好
4~便
5~是
6~晴
7~天
*/
?>

Summary: The above is the entire content of this article, I hope it can be helpful to everyone Learning helps.

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