Summary of examples of 4 loop array methods in PHP

There are many functions that can be used to traverse arrays in php, such as: for statement , list, each, The four functions of foreach are also the main functions for traversing arrays in PHP. They are introduced below.

foreach traverses the array

When we use an array, we often need to traverse the array and obtain each key or element value. PHP provides some special functions for traversing the array. function. Here we first introduce the usage of foreach array traversal function.

Structural form:

foreach ( array_expression as $value ) statement
/* array_expression是要遍历的数组
   as作用是将数组的值赋给$value
   statement是后续语句
*/

Not only the value of the element but also the key name can be obtained through foreach. The structural form:

foreach ( array_expression as $key => $value ) statement

foreach( $color as $c) echo $c ."<br>";

is changed to:

foreach( $color as $key => $c) echo $key.$c ."<br>";

each traverses the array

Traversing the array is an important part of the php array operation. In addition to the foreach function mentioned above, here is another function for traversing the array-each ().

Use each() function to output the key name and corresponding element value of the current pointer position. You can use "0" or "key" to access the key name (identifier), and use "1" or "value" to access the value corresponding to the identifier.

Example:

<?php 
 $languages=array(1=-->"php",
  5=>"html",
  10=>"css");
 $a=each($languages); /* 第一次遍历数组 */  
 echo $a[0] ."t";
 echo $a[1] ."<br>"; 
 $a=each($languages); /* 第二次遍历数组 */
 echo $a[key] ."t";
 echo $a[value];    
?>

list traverses the array

The function list can be assigned to the variable once when traversing the array, usually with Used in conjunction with each() function. Using the list() function makes it easier to access the keys and values ​​returned by each().

Example:

<?php 
 $date=array(1=-->"Monday",
  2=>"Tuesday",
  3=>"Wednesday");
 list($key,$value)=each($date); /* 遍历函数 */
 echo "$key $value" ."<br>"; /* 输出第一个数组 */
 $next=next($date);  /* 指针后移 */
 echo "$next";  
?>

ps: The list() function is just the opposite of the array() function. array() constructs a series of data into an array, while list() splits the array into data.

for traverses the array

In addition to some of the predefined traversal array functions in PHP, we can also use the loop feature of the for statement to traverse the array and output it. Examples are given below:

<?php 
 $a[]="张学友"; /* 定义数组 */
 $a[]="刘德华";
 $a[]="黎明";
 $a[]="郭富城";
 $s=count($a); /* 统计数组个数 */
 for($i=0;$i<$s;$i++){ /* 遍历数组 */
  echo $a[$i] ."<br /-->"; /* 显示数组 */
 }
?>

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