Use of PHP array processing functions array_reduce (ii)

More detailed usage of PHP array operation functions You can also refer to the PHP online reference manual: http://php.net/manual/zh/index.php

array_reduce-iteratively to simplify the array to a single value with a callback function

Given an array:

$ar = Array (1,2,3,4,5);

If the sum of each element in this array is required.

Method One:

It's natural to use foreach to implement

1 $sum = 0; 2 foreach ($aras$v) {3     $sum+ =$v; 4 }5echo$sum;

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Method Two:

We can implement it with array_reduce. It is designed to iterate over algebraic groups. The function receives a maximum of three parameters.

The first parameter receives an array of

The second argument function name, or an anonymous function, has two parameters, representing $result and $item, respectively.

The third parameter, optionally, is treated as the first value in the array, or, if the array is empty, as the final return value.

 1  function  Leijia ( $a ,  $b   2   $a  +=$ b  ;  3  return   $a   4   5   $result  = array_reduce  ( $ar , leijia);  6  $ result ; 

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Continue optimization, you can use the anonymous function above PHP5.3. Make the code more streamlined.

1 $result Array_reduce ($ar ,function($a,$b) {2     $a+ =$b ; 3     return $a ; 4 });

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Array_reduce is not only so powerful. Look at the following example. POPs the first element of the array $arr as the initial value, avoiding the $result being empty in min ($result [' min '], $item [' min ']).

Otherwise the final result min is empty.

1 $arr=Array( 2     Array(' min ' = 1.5456, ' max ' = 2.28548, ' volume ' = 23.152),3     Array(' min ' = 1.5457, ' max ' = 2.28549, ' volume ' = 23.152),4     Array(' min ' = 1.5458, ' max ' = 2.28550, ' volume ' = 23.152),5     Array(' min ' = 1.5459, ' max ' = 2.28551, ' volume ' = 23.152),6     Array(' min ' = 1.5460, ' max ' = 2.28552, ' volume ' = 23.152),7 ); 8 9 $initial=Array_shift($arr); Ten  One $t=Array_reduce($arr,function($result,$item) {  A     $result[' min '] =min($result[' min '],$item[' min ']);  -     $result[' max '] =Max($result[' Max '],$item[' Max ']);  -     $result[' volume '] + =$item[' Volume '];  the  -     return $result;  -},$initial);

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In short, this is more elegant than foreach and defines variables less. Recommended use.

obviously , the previous article (the use of PHP array processing functions Array_push (a)) we can implement this:

1 $ids Array_reduce ($userfunction($v,$w) {2         $v[$w ["id"]] =$w["name"]; 3         return $v ; 4     });

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Implementation results:

Use of PHP array processing functions array_reduce (ii)