数组处理 array_map()

array_map(function,array1,array2,array3...)返回用户自定义函数作用后的数组。回调函数接受的参数数目应该和传递给 array_map() 函数的数组数目一致。

示例：只有一个参数

<?php
function myfunction($v) 
{
    if ($v==="Dog"){
    	return "Fido";
    }
    return $v;
}
$a = array("Horse","Dog","Cat");
print_r(array_map("myfunction",$a));
?>

输出：
Array ( [0] => Horse [1] => Fido [2] => Cat )

两个参数：

<?php
function myfunction($v1,$v2) 
{
    if ($v1===$v2){
    	return "same";
    }
    return "different";
}
$a1 = array("Horse","Dog","Cat");
$a2 = array("Cow","Dog","Rat");
print_r(array_map("myfunction",$a1,$a2));
?>

输出：
Array ( [0] => different [1] => same [2] => different )

自定义函数名设置为 null 时的情况：

<?php
$a1 = array("Dog","Cat");
$a2 = array("Puppy","Kitten");
print_r(array_map(null,$a1,$a2));
?>

输出：
Array (
[0] => Array ( [0] => Dog [1] => Puppy )
[1] => Array ( [0] => Cat [1] => Kitten )
)

使用闭包：

<?php
$a = [];
$b = ["Horse","Dog","Cat"];
 
array_map(function ($value) use (&$a){
    if($value==="Dog"){$a[] = $value;}
},$b);
print_r($a);
 
$a1 = ["Horse","Dog","Cat"];
$a2 = ["Cow","Dog","Rat"];
$a3 = [];
array_map(function ($v1,$v2) use (&$a3) {  
  if($v1==$v2){
      $a3[] = $v1;
  }
},$a1,$a2);

$c = ["Cow","Dog"];
array_map(function ($v1) {
   return $v1.'--1'
},$c);
print_r($c);
?>

输出：
#$a
Array ( [0] => "Dog" )
#$a3
Array ( [0] => "Dog" )
#$c
Array ( [0] => "Cow--1" [1] => "Dog--1")

文章来源于：https://blog.csdn.net/weixin_34233421/article/details/91451175