Common scenarios of using array_flip() to turn values into keys

M66 2025-06-03

The array_flip() function in PHP is a very useful tool. Its function is to swap the keys and values of an array, that is, to use the values in the array as the new key and the original key as the new value. In some scenarios, using array_flip() can greatly simplify the code and improve efficiency. This article will parse the common application scenarios of array_flip() and explain under what circumstances we will use it to convert the value of the array into a key.

1. Use the value as a unique identifier

Suppose we have an array containing multiple user IDs and user names, if we want to use the username as keys and IDs as values, we can use array_flip() to complete this task. This way, the corresponding ID can be quickly obtained through the username.

Sample code:

 <?php
// User data array，The key is the userID，The value is the username
$user_data = array(
    1 => "Alice",
    2 => "Bob",
    3 => "Charlie"
);

// use array_flip() Convert value to key
$flipped_data = array_flip($user_data);

// Output the converted array
print_r($flipped_data);
?>

Output result:

 Array
(
    [Alice] => 1
    [Bob] => 2
    [Charlie] => 3
)

In this example, array_flip() takes the original username as the new key and the user ID as the new value. This makes it easy to find the corresponding user ID based on the user name.

2. Data deduplication or retrieval

array_flip() can also be used for deduplication operations. When an array contains duplicate values, using array_flip() will merge these duplicate values into unique keys. This way, you can easily remove duplicates from the array and get an array with a unique key value.

Sample code:

 <?php
// Array with duplicate values
$values = array("apple", "banana", "apple", "orange", "banana");

// use array_flip() Go to the heavy
$unique_values = array_flip($values);

// 输出Go to the heavy后的数组
print_r($unique_values);
?>

Output result:

 Array
(
    [apple] => 0
    [banana] => 1
    [orange] => 3
)

Through array_flip() , duplicate "apple" and "banana" are removed, leaving only the unique keys.

3. Convert URL parameter array

In some cases, it may be necessary to convert the query parameters of the URL into an array of key-value pairs. array_flip() can help us quickly find the corresponding key from certain parameter values.

Sample code:

 <?php
// Suppose we have one URL Query parameter array
$query_params = array("user_id" => "123", "session_id" => "abc", "page" => "1");

// pass array_flip() Swap keys and values
$flipped_params = array_flip($query_params);

// Output the converted array
print_r($flipped_params);
?>

Output result:

 Array
(
    [123] => user_id
    [abc] => session_id
    [1] => page
)

Here, we use the value of the query parameter as the key, so that we can find the corresponding key in reverse by querying the value of the parameter.