4 Array functions you must know in PHP

In daily development foreach is the syntax we use most, but there are many places that can be completed without foreach, and it is better than foreach Faster. So this article brings you array_filter(),array_map(),array_walk(),array_reduce() Array operation functions. As long as we learn these four functions, we don't need to write so many loop operations during development, and the efficiency is faster than loop values.

array_filter()

$arr = ['a',0,'b','c',1,2,3,4,5,6,7];
//过滤掉所有的数字，只要字符串  减少自己循环的必要
$new_arr = array_filter($arr,function($v){
  if(is_string($v)){
    return $v;
  }
});
print_r($new_arr);
//返回结果
// Array ( [0] => a [2] => b [3] => c )

array_map()

$arr1 = [1,2,3,4,5];
$arr2 = [6,7,8,9,10,55];
 
//函数写前面，数组参数写后面   2个数组的计算，也不需要自己循环计算
$new_arr = array_map(function($val1,$val2){
   return $val1 + $val2;
},$arr1,$arr2);
 
var_dump($new_arr);
//返回结果
//array (size=5)
//  0 => int 7
//  1 => int 9
//  2 => int 11
//  3 => int 13
//  4 => int 15
//  5 => int 55
 
//将数组中的元素用于某种操作
$arr = ['a','b','c','d','e','f',8];
array_walk($arr,function($val,$key){
    echo "{$key} is {$val} <br/>";
});
//返回结果
// 0 is a 
// 1 is b 
// 2 is c 
// 3 is d 
// 4 is e 
// 5 is f 
// 6 is 8

array_walk()

$arr = ['a',0,'b','c',1,2,3,4,5,6,7];
//改变数组中的值，传参的时候使用引用   同意加个连接符3
array_walk($arr,function(&$val,$key){
    $val = $val . 3;
});
var_dump($arr);
// array (size=7)
// 0 => string 'a3' (length=2)
// 1 => string 'b3' (length=2)
// 2 => string 'c3' (length=2)
// 3 => string 'd3' (length=2)
// 4 => string 'e3' (length=2)
// 5 => string 'f3' (length=2)
// 6 => string '83' (length=2)

array_reduce()

//一个数组求和，还可以给第三个参数，作为第一个值
$array = [10,15,20,60];
$as = array_reduce($array,function($k,$v){  
    print_r(&#39;k:&#39;.$k); echo "<br/>";
    print_r(&#39;v:&#39;.$v); echo "<br/>"; 
    return $k + $v;
},50);
print_r(&#39;总计：&#39;.$as);
// k:50
// v:10
// k:60
// v:15
// k:75
// v:20
// k:95
// v:60
// 总计：155echo "<br/>";

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