Reverse key-value operation skills for array_diff_key() + array_flip()

In PHP programming, array operations are very common, and key-value pairs of arrays can be modified or converted in many ways. This article will introduce how to use the array_diff_key() and array_flip() functions to implement reverse key-value operations.

array_flip() function

array_flip() is a very useful PHP built-in function that interchanges keys and values ​​of arrays. That is, it converts keys in the array into values ​​and values ​​into keys. This function is usually very effective when you need to get key and value pairing.

Sample code:

 <?php
$array = array(
    'a' => 1,
    'b' => 2,
    'c' => 3
);

$flipped = array_flip($array);
print_r($flipped);
?>

Output:

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

In the above example, array_flip() exchanges the keys and values ​​of the original array, and finally gets a new array, the value becomes the key, and the key becomes the value.

array_diff_key() function

The array_diff_key() function is used to return elements with different keys in two arrays. It compares the keys of the array, not the values. When performing reverse operations on an array, array_diff_key() can help us remove unnecessary keys, thereby implementing reverse key-value conversion.

Sample code:

 <?php
$array1 = array(
    'a' => 1,
    'b' => 2,
    'c' => 3,
);

$array2 = array(
    'b' => 4,
    'c' => 5,
    'd' => 6,
);

$result = array_diff_key($array1, $array2);
print_r($result);
?>

Output:

 Array
(
    [a] => 1
)

array_diff_key() compares the keys of two arrays and returns a new array containing the key-value pairs in the first array that do not appear in the second array. In this example, 'a' => 1 is the only key-value pair not in the second array.

Combining array_flip() and array_diff_key() to implement reverse key-value operations

By combining array_flip() and array_diff_key() , we can implement more complex key-value operations. Specifically, first use array_flip() to exchange the keys and values ​​of the array, and then use array_diff_key() to compare and remove unnecessary keys, and finally obtain the result of the reverse operation.

Sample code:

 <?php
$array = array(
    'a' => 1,
    'b' => 2,
    'c' => 3,
    'd' => 4,
);

// Swap key-value pairs
$flipped = array_flip($array);

// Suppose we want to remove the key value 2 and 3
$exclude_keys = array(
    2 => 'b',
    3 => 'c',
);

// pass array_diff_key Remove the specified key
$filtered = array_diff_key($flipped, $exclude_keys);

print_r($filtered);
?>

Output:

 Array
(
    [1] => a
    [4] => d
)

In the above code, the key-value pairs of the array are first exchanged through array_flip() , and then the keys with values ​​2 and 3 are removed through array_diff_key() , thereby achieving an inverse operation.

Summarize

By combining array_flip() and array_diff_key() functions, we can easily implement reverse key-value operations. array_flip() is used to swap keys and values, while array_diff_key() can help us remove some unwanted keys as needed. After mastering these techniques, you can process array data more efficiently in actual development.

Thanks for reading! Hopefully this article can help you better understand how to use array_diff_key() and array_flip() in PHP to implement reverse key-value operations. If you have any questions or suggestions, please feel free to leave a message below to discuss.