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

In the process of developing using PHP, we usually encounter the need to convert a two-dimensional array into a one-dimensional array. This requirement is very common in actual development. For example, we need to process data in the database. For some data that needs to be calculated, the queried two-dimensional array is usually converted into a one-dimensional array, which facilitates our calculations.

In PHP, the method of converting a two-dimensional array into a one-dimensional array is very simple and can be done using the array_column() function. Let's take a closer look at how to use the array_column() function.

Basic usage of the array_column() function

The basic syntax of the array_column() function is as follows:

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

This function accepts three parameters, where the $input parameter specifies the array to be converted, the $column_key parameter specifies the column name or key name to be converted into a one-dimensional array, and the $index_key parameter is optional and is used to represent The key name in the new array. If not specified, the numeric index is used.

For example, we have a two-dimensional array as follows:

$users = array(

array('id' => 1, 'name' => 'Tom', 'age' => 20),
array('id' => 2, 'name' => 'Jerry', 'age' => 18),
array('id' => 3, 'name' => 'Lucy', 'age' => 22)

);

We can use the array_column() function to Convert it to a one-dimensional array:

$names = array_column($users, 'name');

The converted result is:

array('Tom' , 'Jerry', 'Lucy')

In the above example, we converted the name field in the $users array into a new one-dimensional array.

In actual development, we may need to convert multiple fields into one-dimensional arrays at the same time. In this case, we can convert multiple fields into one-dimensional arrays respectively, and then splice them together. For example, the following code will convert both the name and age fields into one-dimensional arrays:

$names = array_column($users, 'name');
$ages = array_column($users, 'age') ;
$info = array_merge($names, $ages);

The converted result is:

array('Tom', 'Jerry', 'Lucy', 20, 18, 22)

In the above example, we spliced ​​the $name and $ages arrays together to obtain a new one-dimensional array.

Advanced usage of array_column() function

In addition to the basic usage introduced above, the array_column() function also has some advanced usage, let’s introduce them one by one below.

1. Original array as index

Sometimes we need to use a field in the original array as the index of the new array. In this case, we can call array_column() function, specify the third parameter $index_key as the field name in the original array. For example, to use the id field in the above $users array as the index of the new array, you can do the following:

$users = array(

array('id' => 1, 'name' => 'Tom', 'age' => 20),
array('id' => 2, 'name' => 'Jerry', 'age' => 18),
array('id' => 3, 'name' => 'Lucy', 'age' => 22)

);
$names = array_column($ users, 'name', 'id');

The converted result is:

array(1 => 'Tom', 2 => 'Jerry', 3 => ; 'Lucy')

As you can see, the key name of the new array is the id field in the original array.

2. Processing multi-dimensional arrays

In actual development, we may encounter situations where we need to process multi-dimensional arrays. In this case, we can use the array_map() function to convert each The two-dimensional array is converted into a one-dimensional array, and then the array_merge() function is used to splice them together to obtain a new one-dimensional array. For example:

$users = array(

array('id' => 1, 'name' => array('first' => 'Tom', 'last' => 'Smith'), 'age' => 20),
array('id' => 2, 'name' => array('first' => 'Jerry', 'last' => 'Brown'), 'age' => 18),
array('id' => 3, 'name' => array('first' => 'Lucy', 'last' => 'Johnson'), 'age' => 22)

);
$names = array_map(function($user) {

return $user['name']['first'] . ' ' . $user['name']['last'];

}, $users);
$ages = array_column($users, 'age');
$info = array_merge($names, $ages);

The converted result is:

array( 'Tom Smith', 'Jerry Brown', 'Lucy Johnson', 20, 18, 22)

As you can see, when we convert the name field in the $users array into a one-dimensional array, we need to use array_map( ) function, convert each two-dimensional array into a one-dimensional array, and then splice them together using the array_merge() function.

Summary

Through the introduction of this article, we can see that converting a two-dimensional array into a one-dimensional array is very easy in PHP, just use the array_column() function. If you need to convert multiple fields into a one-dimensional array, you can use the array_column() function multiple times and then splice them together. If you need to index a field in the original array, you can specify the third parameter when calling the array_column() function. If you need to process multi-dimensional arrays, you can use the array_map() function to convert each two-dimensional array to one dimension. arrays and then splice them together using the array_merge() function.

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