How to get the keys of an array in php

In PHP development, array is a very common data type used to store multiple data elements, which are accessed and processed based on index or key value.

For an array, we can not only obtain the value of the element in the array through subscript or index, but also obtain the value of the array element by obtaining the key value corresponding to the element. Therefore, this article will share the relevant knowledge about obtaining array key values ​​in PHP.

1. Common ways to get array keys in PHP

1. Get array keys through foreach loop

Traverse the values ​​in the array through foreach loop, you can get them at the same time The key corresponding to the current value implements the acquisition of array keys.

The following is a sample code:

$fruit = array('apple' =>'5kg', 'banana' => '3kg', 'cherry'=>'2kg');
foreach($fruit as $key => $val){
    echo "键：" . $key . " 值：" . $val . "<br />";
}

The output result is:

键：apple 值：5kg
键：banana 值：3kg
键：cherry 值：2kg

Through the foreach loop, we can traverse the elements in the array in sequence, and the $key variable represents the current The key value corresponding to the element can be obtained by outputting $key.

2. Obtain the array keys through the array_keys() function

PHP provides an array_keys() function, which can return all the key names in an array, and the return value is in the form of an array.

The usage is as follows:

$fruit = array('apple' =>'5kg', 'banana' => '3kg', 'cherry'=>'2kg');
$keys = array_keys($fruit);
print_r($keys);

The output result is:

Array ( [0] => apple [1] => banana [2] => cherry )

3. Obtain the array key through the array_map() function

array_map() in PHP The function can apply a user-defined function to each element in the array and return a new array.

We can achieve the function of obtaining all keys of the array through the array_map() function. The specific implementation method is as follows:

$fruit = array('apple' =>'5kg', 'banana' => '3kg', 'cherry'=>'2kg');
function getKeys($item){
    return $item;
}
$keys = array_map("getKeys", array_keys($fruit));
print_r($keys);

The running result is:

Array ( [0] => apple [1] => banana [2] => cherry )

In the above code, we You need to customize a function getKeys() to obtain key values. This function receives an array element as a parameter and returns the element. Then call the getKeys() function through the array_map() function to achieve the operation of obtaining the array keys.

2. Summary

Obtaining the key of an array is a very common requirement in PHP. In the actual development process, it is often necessary to obtain the key value of an array. This article introduces the three key values ​​​​of an array in PHP. A method, I hope it can help everyone:

1. Get array keys through foreach loop
2. Get array keys through array_keys() function
3. Get through array_map() function Array keys

By using these methods, we can quickly and easily obtain the keys of the array, which brings a lot of convenience to our development.

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