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In PHP, array_flip() is a very practical built-in function. Its function is to exchange the positions of keys and values in the array, change the element originally as keys into values, and the element originally as values into keys. This function is very useful for certain specific scenarios and can greatly improve the efficiency and readability of the code.
array_flip(array $array): array
Parameter description :
$array : The array to be flipped. The keys and values of the array will be interchanged.
Return value :
Returns a new array, the original value in the new array will become a key, and the original key will become a value.
Below is a simple array_flip() function example to help you understand its basic usage.
<?php
// Original array
$original_array = array(
"a" => 1,
"b" => 2,
"c" => 3
);
// use array_flip() Function flip array
$flipped_array = array_flip($original_array);
// Output flipped array
print_r($flipped_array);
?>
Output result :
Array
(
[1] => a
[2] => b
[3] => c
)
In this example, the key-value pairs of the original array a => 1 , b => 2 , c => 3 are flipped to 1 => a , 2 => b , 3 => c .
Key name uniqueness : array_flip() will take the value of the original array as a key, so if there are duplicate values in the original array, one of the values will be lost after flipping. For example:
<?php
$original_array = array(
"a" => 1,
"b" => 2,
"c" => 1
);
$flipped_array = array_flip($original_array);
print_r($flipped_array);
?>
Output result :
Array
(
[1] => c
[2] => b
)
In this example, the value 1 in the original array appears twice, and only the last key c is retained after flipping, and the previous key a is discarded.
The value must be a scalar type : array_flip() can only process values of scalar type, namely integers, floats, strings, etc. If the value in the array is an array or object, array_flip() will throw a warning.
Flipped key type : The flipped key will be determined based on the value type of the original array. If the value of the original array is a string or a number, the flipped key will be a string or a number.
array_flip() is very useful in multiple scenarios. Here are some typical application scenarios:
Suppose you have an array containing the user ID and username, you can reverse it through array_flip() to quickly query the user ID corresponding to the username:
<?php
$users = array(
101 => 'alice',
102 => 'bob',
103 => 'charlie'
);
// pass array_flip() Create a reverse map
$users_flipped = array_flip($users);
// Find 'bob' Users ID
$user_id = $users_flipped['bob'];
echo "Bob Users ID yes: " . $user_id;
?>
Output result :
Bob Users ID yes: 102
When working with configuration files, you may need to quickly access the values of certain configuration items. You can quickly implement the inversion of key-value pairs through array_flip() for easy search.
<?php
$config = array(
'host' => 'localhost',
'db_name' => 'test_db',
'username' => 'root',
'password' => '1234'
);
// Flip the configuration array
$config_flipped = array_flip($config);
echo "Configuration for 'localhost' is: " . $config_flipped['localhost'];
?>
Output result :
Configuration for 'localhost' is: host
When you have an array containing duplicate values, you can use array_flip() to remove duplicates. By flipping the array and then flipping back, the repeated values will be automatically discarded:
<?php
$array_with_duplicates = array(1, 2, 3, 2, 4, 1);
// Go to the heavy
$unique_array = array_flip(array_flip($array_with_duplicates));
print_r($unique_array);
?>
Output result :
Array
(
[1] => 1
[2] => 2
[3] => 3
[4] => 4
)
array_flip() is a simple but powerful PHP function that allows us to swap keys and values of an array. This function is very suitable for scenarios where quick searches or deduplication are required. However, when using it, you need to pay attention to the uniqueness of the value and the limitations of the data type. By using array_flip() properly, you can handle complex array operations in PHP and improve the simplicity and efficiency of your code.
