How to use PHP to convert array key names into key values

In PHP, we often encounter situations where we need to operate on arrays, including the need to convert array key names into key values. This article will introduce how to use PHP to convert array key names into key values.

Array is a commonly used data structure that can save multiple elements and store them in the form of key-value pairs. In PHP, array is a very important data type. It can be used in many situations, such as recording user information, storing database query results, etc.

In some cases, we may need to convert the key names of the array into key values. For example, some APIs require us to convert key names in JSON data into key values ​​in order to parse them correctly. At the same time, some array operations also require key values ​​instead of key names. For example, when using the array_keys function to return the key names of the array, we can use this method to easily get the result of the key value.

The following are several ways to convert array key names into key values:

1. Use foreach loop

Basic idea: By traversing the array, The original key name is used as the key value of the new array, and the original key value is used as the element of the new array. The code is as follows:

$original_array = array("foo" => 1, "bar" => 2, "baz" => 3);
$new_array = array();
foreach ($original_array as $key => $value) {
   $new_array[$value] = $key;
}
print_r($new_array);

The output result is: Array ([1] => foo [2] => bar [3] => baz )

This method passes the foreach loop, The purpose of converting array key names into key values ​​is achieved, and an array with new key values ​​is obtained. It should be noted that if there are multiple elements with the same key value in the original array, only the value corresponding to the key name of the last element will be retained in the new array, and the rest will be overwritten.

2. Use the array_flip function

Basic idea: use the array_flip function to flip the key names and key values ​​​​of the original array, that is, convert the key names into key values, and convert the key values ​​into Key name. The code is as follows:

$original_array = array("foo" => 1, "bar" => 2, "baz" => 3);
$new_array = array_flip($original_array);
print_r($new_array);

The output result is: Array ([1] => foo [2] => bar [3] => baz )

This method uses the array_flip function , flipping the key names and key values ​​of the original array, realizing the interchange of key names and key values. It should be noted that this function will merge the same values ​​in the original array into one element, and will only retain the key name of the last element as the key name of the new array, and will not retain the key name of any element in the original array.

3. Use the array_map function

Basic idea: Use the array_map function to process the key name of each element, and use the original key name as the key value of the new array. The code is as follows:

$original_array = array("foo" => 1, "bar" => 2, "baz" => 3);
$new_array = array_map(function($key){return $key;}, $original_array);
print_r($new_array);

The output result is: Array ([0] => foo [1] => bar [2] => baz )

This method uses the array_map function , process the key name of each element and use it as the key value of the new array, achieving the purpose of converting the array key name into a key value. It should be noted that the array returned by this method does not use the key values ​​of the original array as the elements of the new array, but uses numbers from 0 to n as the key values ​​of the new array. You need to choose whether to use this method according to specific needs.

Summary:

This article introduces three methods to convert array key names into key values, which are implemented through foreach loop, array_flip function and array_map function respectively. It is necessary to choose the corresponding method to solve the problem according to the specific needs. At the same time, you also need to pay attention to the duplication of key names in the array, as well as the numerical index problem of the array returned by the array_map function.

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