How to convert two-dimensional array to one-dimensional array in php

php Method to convert a two-dimensional array to a one-dimensional array: 1. Use the array_column() function; 2. Use the array_walk() function; 3. Use the array_map() function; 4. Use the array_reduce() function; 5 , use array_walk_recursive() function.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Summary of converting two-dimensional array to one-dimensional array

For example, convert the following two-digit array into a one-dimensional array

$records = [
    [
        'id' => 2135,
        'first_name' => 'John',
        'last_name' => 'Doe',
    ],
    [
        'id' => 3245,
        'first_name' => 'Sally',
        'last_name' => 'Smith',
    ],
    [
        'id' => 5342,
        'first_name' => 'Jane',
        'last_name' => 'Jones',
    ],
    [
        'id' => 5623,
        'first_name' => 'Peter',
        'last_name' => 'Doe',
    ]
];

1.array_column()

array_column() is PHP built-in functions, the restriction is that the PHP version must be 5.5.0 and above!

Example 1:

<?php
$first_names = array_column($records, &#39;first_name&#39;);
var_dump($first_names);
?>

The print result is:

##Example 2:

<?php
$first_names = array_column($records, &#39;first_name&#39;,&#39;id&#39;);
var_dump($first_names);
?>

The print result is:

2.array_walk()

array_walk() function uses a user-defined function to Callback processing is performed on each element to implement the current function:

$first_names= [];
array_walk($records, function($value, $key) use (&$first_names){
    $first_names[] = $value['first_name'];
});
var_dump($first_names);

The printed result is:

3.array_map()

The array_map() function is similar to array_walk(), applying the callback function to the cells of the given array.

$first_names= [];
array_map(function($value) use (&$first_names){
    $first_names[] = $value['first_name'];
}, $records);
var_dump($first_names);

The printed result is:

4.array_reduce()

array_reduce — Use a callback function to iteratively reduce an array to a single value.

$first_names = array_reduce($records,function($result, $value){
    array_push($result, $value['first_name']);
    return $result;
},[]);
var_dump($first_names);

Print results:

5. array_walk_recursive()

array_walk_recursive — Applies the user function recursively to each member of the array. This function can convert an array of any dimension into a one-dimensional array.

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