Summary of usage of php array operations

php defines arrays

<?php  
    $array = []; 
    $array["key"] = "value"; 
 ?>

There are two main ways to declare arrays in PHP:

1. Declare arrays using the array() function.

2. 2. Directly assign values ​​to array elements.

<?php    
    //array数组
    $users = [&#39;a&#39;,&#39;b&#39;,&#39;c&#39;,&#39;d&#39;];
    echo $users;//只会打印出数据类型Arra
    print_r($users);//Array ( [0] => a[1] => b[2] => c[3] => d)
    $numbers = range(1,5);//创建一个包含指定范围的数组
    print_r($numbers);//Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 )
    print_r(true);//1
    var_dump(false);//bool(false)//print_r可以把字符串和数字简单地打印出来，数组会以Array开头并已键值形式表示，print_r输出布尔值和null的结果没有意义，因此用var_dump更合适

//Display all the values ​​in the array through loops

  for($i = 0 ;$i < 5;$i++){
        echo $users[$i];
        echo &#39;<br/>&#39;;
    }

//Use count/sizeof to count the number of units in the array or the number of attributes in the object

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

//You can also traverse the array through a foreach loop. The advantage is that you don’t need to consider the key

 foreach($users as $value){
    echo $value.&#39;<br/>&#39;;//点号为字符串连接符号
 }
//foreach循环遍历 $key => $value；$key和$value是变量名，可以自行设置
 foreach($users as $key => $value){
    echo $key.&#39;<br/>&#39;;//输出键
 }
?>

Create an array with custom keys

Usage of

<?php
    // 创建自定义的数组
    $array = ["a"=>1,"b"=>2,"c"=>3,"d","e"];
    //如果没有声明键，它会从零开始
    print_r($array);//array([a]=>1,[b]=>2,[c]=>3,[0]=>d,[1]=>e);
?>

each()

  <?php    
        //通过为数组元素赋值来创建数组
        $array[&#39;key&#39;] = 22;
        echo $array.&#39;<br/>&#39;;//Array
        //因为相关数组的索引不是数字，所以无法通过for循环来进行遍历操作，只能通过foreach循环或list()和each()结构
        //each的使用
        //each返回数组中当前的键/值对并将数组指针向前移动一步
        $users = array(&#39;key&#39;=>22,&#39;key1&#39;=>20,&#39;key2&#39;=>30);
        //print_r(each($users));//Array ( [1] => 22 [value] => 22 [0] => array[key] => array)
        //相当于：$a = array([0]=>array,[1]=>22,[value]=>22,[key]=>array);
    $a = each($users);//each把原来的数组的第一个元素拿出来包装成新数组后赋值给$a
    echo $a[0];//array    //!!表示将真实存在的数据转换成布尔值
    echo !!each($users);//1
    ?>

## The pointer of each points to the first key-value pair and returns For the first array element, get its key-value pair and package it into a new array

Use of list()

list is used to use the array Assign values ​​to some variables, see the following example:

    <?php        
    $a = [&#39;2&#39;,&#39;abc&#39;,&#39;def&#39;];
       list($var1,$var2) = $a;
        echo $var1.&#39;<br/>&#39;;//2
       echo $var2;//abc        
       $a = [&#39;name&#39;=>&#39;trigkit4&#39;,&#39;age&#39;=>22,&#39;0&#39;=>&#39;boy&#39;];
     //list只认识key为数字的索引
      list($var1,$var2) = $a;
      echo $var1;//boy
    ?>

Note: list only recognizes indexes whose keys are numbers

Sorting of array elements

## Reverse sorting: sort(), asort() and ksort() are all forward Sorting, of course, also has a corresponding reverse sorting.

Implementation of reverse: rsort(), arsort() and krsort().

The array_unshift() function adds new elements to the head of the array, and the array_push() function adds each new element to the end of the array.

        array_shift()删除数组头第一个元素,与其相反的函数是 array_pop(),删除并返回数组末 尾的一个元素。

        array_rand()返回数组中的一个或多个键。

        函数shuffle()将数组个元素进 行随机排序。

        函数 array_reverse()给出一个原来数组的反向排序

    数组的各类API的使用

    注：count()和 sizeof()统计数组下标的个数
    array_count_values()统计数组内下标值的个数

 <?php
        $numbers = array(&#39;100&#39;,&#39;2&#39;);
       sort($numbers,SORT_STRING);//按字符串排序，字符串只比较第一位大小
        print_r($numbers);//Array ( [0] => 100 [1] => 2 )
        $arr = array(&#39;trigkit4&#39;,&#39;banner&#39;,&#39;10&#39;);
        sort($arr,SORT_STRING);
        print_r($arr);//Array ( [0] => 10 [1] => banner [2] => trigkit4 )
        shuffle($arr);
        print_r($arr);//随机排序
        $array = array(&#39;a&#39;,&#39;b&#39;,&#39;c&#39;,&#39;d&#39;,&#39;0&#39;,&#39;1&#39;);
        array_reverse($array);
        print_r($array);//原数组的反向排序。 Array ( [0] => a [1] => b [2] => c [3] => d [4] => 0 [5] => 1 )
  ?>

       //数组的拷贝
       

        $arr1  = array( '10' , 2);
     $arr2  =  &$arr1 ;
     $arr2 [] =  4 ;  // $arr2 被改变了,$arr1仍然是array('10', 3)
     print_r($arr2);//Array ( [0] => 10 [1] => 2 [2] => 4 )

   //asort的使用
      

 $arr3  = & $arr1 ;//现在arr1和arr3是一样的
  $arr3 [] =  '3' ;
  asort($arr3);//对数组进行排序并保留原始关系
  print_r($arr3);// Array ( [1] => 2 [2] => 3 [0] => 10 )

   //ksort的使用
     

  $fruits = array('c'=>'banana','a'=>'apple','d'=>'orange');
   ksort($fruits);
   print_r($fruits);//Array ( [a] => apple [c] => banana [d] => orange )

  //unshift的使用
      

    array_unshift($array,'z');//开头处添加一元素
  print_r($array);//Array ( [0] => z [1] => a [2] => b [3] => c [4] => d [5] => 0 [6] => 1 )

   //current(pos)的使用
     

  echo current($array);//z;获取当前数组中的当前单元

   //next的使用
      

 echo next($array);//a;将数组中的内部指针向前移动一位

   //reset的使用
      

 echo reset($array);//z;将数组内部指针指向第一个单元

   //prev的使用
     

  echo next($array);//a;
   echo prev($array);//z;倒回一位

 //sizeof的使用
        echo sizeof($array);//7；统计数组元素的个数
    //array_count_values
        $num = array(10,20,30,10,20,1,0,10);//统计数组元素出现的次数
        print_r(array_count_values($num));//Array ( [10] => 3 [20] => 2 [30] => 1 [1] => 1 [0] => 1 ) ?>

    urrent()：每个数组都有一个内部指针指向他的当前单元，初始指向插入到数组中的第一个元素

    for循环遍历

 <?php
       $value = range(0,120,10);
        for($i=0;$i<count($value);$i++){
        print_r($value[$i].&#39; &#39;);//0 10 20 30 40 50 60 70 80 90 100 110 120 
    }?>

    数组的实例

    array_pad函数的使用

    <?php   
     //array_pad函数，数组数组首尾选择性追加        
     $num = array(1=>10,2=>20,3=>30);        
     $num = array_pad($num,4,40);        
     print_r($num);//Array ( [0] => 10 [1] => 20 [2] => 30 [3] => 40 )        
     $num = array_pad($num,-5,50);//array_pad(array,size,value)        
     print_r($num);//Array ( [0] => 50 [1] => 10 [2] => 20 [3] => 30 [4] => 40 ) 
     ?>

    size:指定的长度。整数则填补到右侧，负数则填补到左侧。

    unset()的使用

 <?php    
    //unset()的使用        
    $num = array_fill(0,5,rand(1,10));//rand(min,max)        
    print_r($num);//Array ( [0] => 8 [1] => 8 [2] => 8 [3] => 8 [4] => 8 )         
    echo &#39;<br/>&#39;;        
    unset($num[3]);        
    print_r($num);//Array ( [0] => 8 [1] => 8 [2] => 8 [4] => 8 ) 
    ?>

 array_fill()的使用

 <?php   
     //array_fill()的使用        
     $num = range(&#39;a&#39;,&#39;e&#39;);        
     $arrayFilled = array_fill(1,2,$num);//array_fill(start,number,value)        
     echo &#39;<pre class="brush:php;toolbar:false">&#39;;        
     print_r($arrayFilled);
     ?>

array_combine()的使用

         <?php
        $number = array(1,2,3,4,5);
        $array = array("I","Am","A","PHP","er");
        $newArray = array_combine($number,$array);
        print_r($newArray);//Array ( [1] => I [2] => Am [3] => A [4] => PHP [5] => er ) 
        ?>

array_splice()删除数组成员

 <?php
        $color = array("red", "green", "blue", "yellow");
        count ($color); //得到4
        array_splice($color,1,1); //删除第二个元素
        print_r(count ($color)); //3
        echo $color[2]; //yellow
        echo $color[1]; //blue?>

 array_unique删除数组中的重复值

 <?php
        $color=array("red", "green", "blue", "yellow","blue","green");
        $result = array_unique($color);
        print_r($result);//Array ( [0] => red [1] => green [2] => blue [3] => yellow ) ?>

 array_flip()交换数组的键值和值

  <?php
       $array = array("red","blue","red","Black");
        print_r($array);
        echo "<br />";
        $array = array_flip($array);//
        print_r($array);//Array ( [red] => 2 [blue] => 1 [Black] => 3 ) ?>

 array_search()搜索数值

 <meta charset="utf-8">
    <?php       
    $array = array("red","blue","red","Black");      
    $result=array_search("red",$array)//array_search(value,array,strict)
        if(($result === NULL)){        
        echo "不存在数值red";        
        }else{            
        echo "存在数值 $result";//存在数值 0         
        }
    ?>

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