How to get the keys of an array in php

PHP is a very popular programming language that supports various data types and data structures. In PHP, an array is a very commonly used data structure that can store multiple values ​​and access these values ​​using keys. In this article, we will take a deep dive into how to get the keys of an array in PHP.

Getting the keys of an array

In PHP, there are many different ways to get the keys of an array. Here are some of the most commonly used methods:

1. Use the array_keys() function

The array_keys() function returns a new array consisting of all the key names in the array. This function accepts an array as argument and returns a new array containing only the key names. The following is an example:

$arr = array('a' => 1, 'b' => 2, 'c' => 3);
$keys = array_keys($arr);
print_r($keys);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
)

2. Using foreach loop

The foreach loop is one of the most commonly used loop structures in PHP. You can easily iterate through all elements in an array using a foreach loop. During the traversal process, we can use the key of the current element to get the key name of this element. The following is an example:

$arr = array('a' => 1, 'b' => 2, 'c' => 3);
foreach ($arr as $key => $value) {
    echo $key . "\n";
}

Output result:

a
b
c

3. Use the combination of array_keys() foreach loop

Use the array_keys() function to get the key array of the array, and then Using a foreach loop to traverse the key array, you can easily obtain the keys of the array. The following is an example:

$arr = array('a' => 1, 'b' => 2, 'c' => 3);
$keys = array_keys($arr);
foreach ($keys as $key) {
    echo $key . "\n";
}

Output result:

a
b
c

4. Use the array_map() function

array_map() function can perform a specification for each element in the array callback function and returns a new array containing the return value of each element. We can use the array_map() function to get the key array of the array. Here is an example:

$arr = array('a' => 1, 'b' => 2, 'c' => 3);
$keys = array_map(function($k){ return $k; }, array_keys($arr));
print_r($keys);

Output:

Array
(
    [0] => a
    [1] => b
    [2] => c
)

Summary

In PHP, there are many different ways to get the keys of an array. The most common methods are to use the array_keys() function, foreach loop and array_map() function. We can choose the appropriate method to obtain the keys of the array according to specific scenarios and needs. Mastering these methods can improve our efficiency and convenience when processing arrays in PHP.

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