php array reset key code

In PHP, an array is a data structure used to store a group of similar data items. Each data item has a key and a value. The key is the unique identifier used to identify the data item, and the value is the actual data item value. Sometimes, we need to reset the key codes in the array, this can be done by using some PHP built-in functions.

Arrays in PHP can be created in two ways: associative arrays and indexed arrays. In an associative array, we can manually assign a unique key name to each data item, while in an indexed array, a numeric index is used to identify each data item.

In an associative array, if we want to reset the key code, we can use the array_keys(), array_values() and array_combine() functions. Here is an example of using these functions to reset an associative array:

1. Regenerate the index using array_values()

$fruits = array('a'=> 'apple', 'b'=> 'banana', 'c'=> 'cherry');
$fruits = array_values($fruits);
print_r($fruits);

The above code will output the following results:

Array
(
    [0] => apple
    [1] => banana
    [2] => cherry
)

In this example, we use the array_values() function to regenerate the old associative array into a new indexed array. Each item in the new array will be rekeyed as a numerical index, starting at 0 and going up to the number of the last element.

2. Use array_keys() to regenerate key names

$fruits = array('a'=> 'apple', 'b'=> 'banana', 'c'=> 'cherry');
$keys = array_keys($fruits);
$new_keys = array('x', 'y', 'z');
$fruits = array_combine($new_keys, $fruits);
print_r($fruits);

The above code will output the following results:

Array
(
    [x] => apple
    [y] => banana
    [z] => cherry
)

In this example, we first use array_keys () gets all the keys in the old array, and then uses the array_combine() function to combine these keys with the values ​​in the new array. The array function array_combine() takes two arrays as input and returns a new array, where the values ​​in the first array represent the keys of the new array and the values ​​in the second array represent the values ​​of the new array. Therefore, we can use this function to regenerate an associative array into an associative array with new keys.

In the index array, we need to use the array_values() and array_combine() functions to reset the key code. Here is an example of using these functions to reset an indexed array:

3. Generate a new index using array_values()

$fruits = array('apple', 'banana', 'cherry');
$fruits = array_values($fruits);
print_r($fruits);

The above code will output the following result:

Array
(
    [0] => apple
    [1] => banana
    [2] => cherry
)

In this example, we use the array_values() function to regenerate the old index array into a new index array. Each item in the new array will be rekeyed as a numerical index, starting at 0 and going up to the number of the last element.

4. Use array_combine() to generate a new index

$fruits = array('apple', 'banana', 'cherry');
$new_keys = array('x', 'y', 'z');
$fruits = array_combine($new_keys, $fruits);
print_r($fruits);

The above code will output the following results:

Array
(
    [x] => apple
    [y] => banana
    [z] => cherry
)

In this example, we use array_combine( ) function regenerates the old index array into a new associative array. We use the new key array as the key of the new array, and the value corresponding to each element in the original array becomes the value of the new array. With this approach we can regenerate the indexed array into an associative array with new keys.

Summary

In this article, we introduced how to rekey an array using built-in functions in PHP. Whether it is an associative array or an index array, we can use these functions to generate new key codes. This technique can be used to fix performance bottlenecks that occur when reading very large arrays, because unreasonable key codes cause array access speeds to slow down. Therefore, we should always look for opportunities to optimize array keys to improve the performance and efficiency of our PHP applications.

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