How to implement key-value merging in PHP using array_flip() and array_merge()?

In PHP, arrays are very important data structures. We often need to process arrays, especially when dealing with key-value pairs. In many cases, we need to combine multiple numbers, and sometimes even need to exchange key values. PHP provides built-in functions such as array_flip() and array_merge() to help us implement these functions. This article will explain how to use these two functions to implement key-value merging in PHP.

1. Basic usage of array_flip() function

The array_flip() function is used to swap keys and values ​​in an array. It inverts all keys in the array as values ​​and all values ​​as keys. It should be noted that if there are duplicate values ​​in the array, array_flip() will overwrite the previous key.

 <?php
// Example array
$array = [
    'a' => 'apple',
    'b' => 'banana',
    'c' => 'cherry'
];

// use array_flip() Reverse key value
$flippedArray = array_flip($array);

// Output inverted array
print_r($flippedArray);
?>

Output:

 Array
(
    [apple] => a
    [banana] => b
    [cherry] => c
)

With array_flip() , we successfully swap the keys and values ​​of the original array.

2. Basic usage of array_merge() function

The array_merge() function is used to merge one or more arrays. If there is the same key in the array, it overwrites the previous value with the values ​​in the subsequent array. array_merge() reindexes the numeric array, retaining the keys of the associative array.

 <?php
// Example array
$array1 = [
    'a' => 'apple',
    'b' => 'banana'
];

$array2 = [
    'c' => 'cherry',
    'd' => 'date'
];

// Merge arrays
$mergedArray = array_merge($array1, $array2);

// Output the merged array
print_r($mergedArray);
?>

Output:

 Array
(
    [a] => apple
    [b] => banana
    [c] => cherry
    [d] => date
)

With array_merge() we combine two arrays into an array, and retain their respective key-value pairs.

3. Merge key values ​​using array_flip() and array_merge()

Now we can use array_flip() and array_merge() in combination to implement more complex key-value merging operations. For example, we have two arrays, each of which needs to be merged with the keys of another array. In this case, we first use array_flip() to invert the array, and then use array_merge() to merge the two inverted arrays.

 <?php
// Example array
$array1 = [
    'a' => 'apple',
    'b' => 'banana'
];

$array2 = [
    'apple' => 'fruit',
    'banana' => 'fruit'
];

// use array_flip() Invert the array
$flippedArray1 = array_flip($array1);
$flippedArray2 = array_flip($array2);

// use array_merge() Merge and inverted arrays
$mergedArray = array_merge($flippedArray1, $flippedArray2);

// Output the final merged array
print_r($mergedArray);
?>

Output:

 Array
(
    [apple] => a
    [banana] => b
    [fruit] => apple
)

4. Practical application

Sometimes we need to merge arrays according to different conditions. In this case, we can customize how to use array_flip() and array_merge() according to our needs. For example, we can merge two arrays of data obtained from different URLs (assuming that the original array contains information about the URL).

 <?php
// The obtained data array
$array1 = [
    'https://example.com/page1' => 'Page 1',
    'https://example.com/page2' => 'Page 2'
];

$array2 = [
    'https://example.com/page3' => 'Page 3',
    'https://example.com/page4' => 'Page 4'
];

// pass array_flip() Invert the array并合并
$flippedArray1 = array_flip($array1);
$flippedArray2 = array_flip($array2);

// Merge two inverted arrays
$mergedArray = array_merge($flippedArray1, $flippedArray2);

// Replace the domain name as m66.net
foreach ($mergedArray as $key => $value) {
    $mergedArray[$key] = str_replace('example.com', 'm66.net', $value);
}

// Output the final result
print_r($mergedArray);
?>

Output: