How to flip the order of subscripts in an array in php

In PHP development, we often need to operate arrays. Array is a very powerful data type that can hold multiple values ​​and access these values ​​through subscripts. Usually, we use numbers as subscripts in arrays. But sometimes, we need to use other data types as subscripts. In this case, we need to flip the order of the subscripts in the array.

In PHP, flipping the subscripts of an array is a common task. This means that, in an array, we need to change the values ​​of the subscripts to the values ​​they currently point to. Typically, we would use a loop to iterate over the array, and then use a new array to store the new value of each element on each iteration.

Here is an example that demonstrates how to flip the subscripts of an array:

$old_array = array('apple' => 1, 'banana' => 2, 'orange' => 3);
$new_array = array();
foreach ($old_array as $key => $value) {
    $new_array[$value] = $key;
}
print_r($new_array);

In the above example, we first define an array containing three elements. We then use a loop to iterate through this array. In each iteration, we swap the indexes and values ​​of the elements in the old array and save them into a new array. When the entire old array is traversed, we get a new array whose subscript is the value in the original array, and the value is the subscript in the original array. Finally, we use the print_r function to print out the new array.

The output result is as follows:

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

It can be seen from the output result that the subscript in the new array has become the value in the old array, and the value has become the subscript in the old array .

In addition to the above example, we can also use PHP's own array_flip function to flip the subscript of the array. This function is a very handy tool for using values ​​in an array as keys and keys in an array as values. Using the array_flip function allows us to flip the index of the array more conveniently without writing a loop.

Here is an example of flipping the index of an array using the array_flip function:

$old_array = array('apple' => 1, 'banana' => 2, 'orange' => 3);
$new_array = array_flip($old_array);
print_r($new_array);

In this example, we first define an old array with three elements. We then pass this array to the array_flip function. This function returns a new array in which the keys of the original array become values ​​and the values ​​of the original array become keys. Finally, we use the print_r function again to print out the new array.

The output result is as follows:

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

It can be seen from this output result that using PHP's built-in array_flip function can also easily flip the subscript of the array, and does not A loop needs to be written.

To summarize, flipping the subscripts of an array is a common task, and there are multiple ways to accomplish it in PHP. The most common method is to use a loop to iterate through the array and then swap the index and value of each element. And we can also use the built-in array_flip function to quickly flip the index of the array. No matter which method, we can easily operate and process arrays.

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