Detailed explanation of php array function-PHP Tutorial-php.cn

Detailed explanation of php array function

小云云

Release： 2023-03-22 18:16:02

Original

1986 people have browsed it

This article mainly shares with you the detailed explanation of PHP array functions, mainly in the form of code and text. I hope it can help you.

Array

The array belongs to composite type data
The array is actually a Ordered mapping

Classification

索引数组     数组的下标（key）是数字

关联数组     数组的下标（key）是字符串

Copy after login

Whether it is an index array or an associative array, the value is found through the key.

Create

array() form

Create index array

array(value1,value2,value3...)

Copy after login

Example 1

// 通过array()创建下标连续的索引数组
$arr1 = array(&#39;A&#39;,2,false); 

输出结果：
    Array ( [0] => A [1] => 2 [2] => )
    false转换成空字符串

Copy after login

Example 2

//创建手动指定下标的数组
$arr2 = array(2=>&#39;a&#39;,3=>true);

输出结果：
    Array ( [2] => a [3] => 1 )

Copy after login

Create associative array

array(key1=>value1, key2=>value2, key3=>value3...)

Copy after login

Example

// 定义关联数组
$userInfo = array(
    &#39;username&#39;=>&#39;Tim&#39;,
    &#39;age&#39;=>23,
    &#39;email&#39;=>&#39;404491216@qq.com&#39;
);

print_r($userInfo);

输出结果：
    Array ( [username] => Tim 
            [age] => 23 
            [email] => 404491216@qq.com 
          )

Copy after login

[ ] form ( New in 5.4)

$arr = [value1,value2,value3...]

Copy after login

Example

// []创建数组
$arr = [&#39;A&#39;,&#39;B&#39;,true,2];
print_r($arr);

输出结果：
    Array ( [0] => A [1] => B [2] => 1 [3] => 2 )

Copy after login

rang()

is used to create an index array with consecutive subscripts.

range(min, max(, 步进制))

Copy after login

Step system: how much each value differs from, the default is 1.

Example

// range()例子  值为1-10
$arr = range(1,10,2);
print_r($arr);

输出结果：
    Array
        (
            [0] => 1
            [1] => 3
            [2] => 5
            [3] => 7
            [4] => 9
        )

Copy after login

compact()

compact(&#39;变量名&#39;)

Copy after login

is used to create an associative array.

First define it in an external variable, and then pass in the variable to generate an array.

Note that variable names need to be enclosed in quotes.

Example

// compact()例子
$username = &#39;Tim&#39;;
$age = 23;
$email = &#39;xxx@xx.com&#39;;

// 注意，这里变量名需要用引号
$userInfo = compact(&#39;username&#39;,&#39;age&#39;,&#39;email&#39;);

输出结果：
    Array ( [username] => Tim [age] => 23 [email] => xxx@xx.com )

Copy after login

define()

define(key,value)

Copy after login

Example

define(&#39;TEST1&#39;,array(&#39;a&#39;,&#39;b&#39;,&#39;c&#39;));
print_r(TEST1);

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

Copy after login

Loop

for loop

The for loop can only traverse index arrays with consecutive subscripts

Supplement:

count() gets the number of parameters in the array

If it is null, count() will return 0.

Example

// 使用rang()快速创建数组
$arr = range(&#39;a&#39;,&#39;d&#39;);

for($i=0; $i<$len; $i++){
    echo $arr[$i],&#39;<br/>&#39;;
}

输出结果：
    a,b,c,d

Copy after login

for each loop

只要value
foreach (数组名称 as $value)    

key和value 都要
foreach (数组名称 as $key => $value)

Copy after login

Note:

Traverses the empty array, the loop body will not be executed;
When traversing for each, a copy of the array is operated (php7 new feature)
Traversing by reference has better iteration characteristics. Modification of the array will affect the loop (php7)

Example

// php7新特性——foreach操作的是数组的副本
$arr = [0,1,2];
$ref =&$arr;

foreach($arr as $v){
    echo $v,&#39;<br/>&#39;;

    // 老版本会删除1，但php7操作的是副本，所以没影响
    unset($arr[1]);
}

foreach输出结果：
    0 1 2

// 都是0、2   因为1被删除了
var_dump($arr,$ref);  

var_dump输出结果：
array (size=2)
  0 => int 0
  2 => int 2
)

Copy after login

Related recommendations:

Summary of common array functions in php

The above is the detailed content of Detailed explanation of php array function. For more information, please follow other related articles on the PHP Chinese website!