Analysis of the Relationship between array_map and array_column in PHP

This article mainly introduces the Relationship Analysis Between array_map and array_column in PHP. It is a practical concept for beginners of PHP. For more information, see

This article mainly introduces the Relationship Analysis Between array_map and array_column in PHP. It is a practical concept for beginners of PHP. For more information, see

This article analyzes the relationship between array_map and array_column in PHP as an example. The specific analysis is as follows:

The usage of array_map () and array_column () is as follows:

Array_map (); calls the callback function to the unit of the given array.
Array_column (); quick implementation: convert a two-dimensional array into a one-dimensional array

The format of the array_column () function is:

Array array_column (array $ input, mixed $ column_key [, mixed $ index_key]);

Returns the columns whose values are column_key. If the optional parameter index_key is specified, the corresponding key in the returned array corresponds to the value of index_key in the input array.

Sample Code 1:

$ Records = 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:

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

Sample Code 2:

$ Last_names = array_column ($ records, 'last _ name', 'id'); print_r ($ last_names );

Output:

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

If the array_column () function is not available,

Use array_map () to implement Example 1:

$ A = array_map (function ($ element) {// $ records as the parameter to pass in the callback function return $ element ['last _ name']; // return the last_name value of the array element value}, $ records); // array_map returns an array, which is equivalent to storing each $ element ['last _ name'] into a new array, therefore, it is a new index.

Use foreach For Example 1:

Foreach ($ records as $ v) {$ B [] = $ v ['last _ name'];}

Use foreach For Example 2: $ c = array (); foreach ($ records as $ k => $ v) {$ c + = array ($ v ['id'] => $ v ['last _ name']); // use the + operator, in the form of appending (without changing the original array index), merged and assembled arrays} // If array_merge is used, the number key name will be re-numbered

In a typical two-dimensional array, array_column () can be used to match a single value with a value in the retrieved data, however, in the face of complicated array structures, foreach can make you more flexible, but the first choice is to use system functions first.

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