Analysis of the relationship between Array_map and Array_column in PHP

Analysis of the relationship between Array_map and Array_column in PHP

Submission: shichen2014 font: [Increase decrease] Type: Reprint time: 2014-08-19 I want to comment

This article mainly introduces the relationship between Array_map and Array_column in PHP, for PHP Beginners is a more practical concept, the need for friends can refer to the following

This paper analyzes the relationship between Array_map and Array_column in PHP by example, and analyzes the following:

Array_map () and Array_column () use the following:

Array_map (); function The callback function on the cell of the given array
Array_column (); Fast implementation: converting two-dimensional arrays to one-dimensional arrays

The format of the Array_column () function is:

Array Array_column (array $input, mixed $column _key [, Mixed $index _key]);

Returns a column with a value of Column_key in the input array; If an optional parameter index_key is specified, the corresponding key in the returned array is the value of the input array value Index_key.

Example code one:

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$records = array(  array(    ‘id‘ => 2135,    ‘first_name‘ => ‘John‘,    ‘last_name‘ => ‘Doe‘,  ),  array(    ‘id‘ => 3245,    ‘first_name‘ => ‘Sally‘,    ‘last_name‘ => ‘Smith‘,  ),  array(    ‘id‘ => 5342,    ‘first_name‘ => ‘Jane‘,    ‘last_name‘ => ‘Jones‘,  ),  array(    ‘id‘ => 5623,    ‘first_name‘ => ‘Peter‘,    ‘last_name‘ => ‘Doe‘,  )); $first_names = array_column($records, ‘first_name‘);print_r($first_names);

Output:

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1234567

Array(  [0] => John  [1] => Sally  [2] => Jane  [3] => Peter)

Example code two:

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12	$last_names= array_column($records, ‘last_name‘, ‘id‘);print_r($last_names);

Output:

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1234567

Array(  [2135] => Doe  [3245] => Smith  [5342] => Jones  [5623] => Doe)

When no Array_column () function is in the case,

Use Array_map () to implement example one:

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$a = array_map ( function ( $element Code class= "PHP Comments" data-garbage= "true" >//$records passed in as a parameter to the callback function return $element [　　Code class= "PHP string" > ' last_name ' ); //returns the last_name corresponding value of the array element },　　　　　　　　　　　　 $records ); //array_map returns an array, equivalent to depositing each $element[' last_name ' into a new array, Therefore, the new index

Use the Foreach implementation example one:

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1234	foreach($recordsas$v){  $b[] = $v[‘last_name‘];}

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123456

使用foreach实现例二：$c = array();foreach($records as $k=>$v){　$c += array($v[‘id‘]=>$v[‘last_name‘]); //使用+运算符, 以追加的形式(不改变原数组索引), 合并组装的数组}　　　　　　　　　　　　　　　　　//若使用array_merge，数字键名将被重新编号

A typical two-dimensional array in the fetched data, Array_column () can be done with a single value corresponding to the value in the data, but in the case of a more complex array structure, foreach will make you more flexible, but it is always preferred to use system functions first.

Analysis of the relationship between Array_map and Array_column in PHP