How to reverse an array in php

In the PHP programming language, array is a commonly used data type. When performing array operations, we sometimes need to reverse the order of elements in the array. We can use PHP built-in functions to achieve this purpose. This article will introduce how to use PHP to reverse an array. The functions involved include array_reverse() and array_flip().

1. array_reverse() function

array_reverse() function is a built-in function in PHP for reversing an array. The syntax is as follows:

array array_reverse (array $array, bool $preserve_keys = false)

Parameter description:

$array: indicates to reverse The reversed array;

$preserve_keys: If the value of this parameter is true, the key names of the original array will be retained in the reversed array. The default is false.

Example demonstration:

$fruits = array( "apple", "banana", "orange", "lemon" ); $reverse_fruits = array_reverse($fruits); print_r($reverse_fruits);

Output result:

Array ( [0] => lemon [1] => orange [2] => banana [3] => apple )

2. array_flip() function

array_flip() function is used in PHP Built-in function for exchanging keys and values in an array. If the keys and values in the array are not repeated, you can use this function to easily interchange the keys and values in the array. The operation of reversing an array essentially swaps the index value of the array with its corresponding value. Therefore, using the array_flip() function can also achieve the effect of array reversal.

The syntax of the array_flip() function is as follows:

array array_flip (array $array)

Parameter description:

$array : Indicates the array to be reversed.

Example demonstration:

$fruits = array( "apple", "banana", "orange", "lemon" ); $flip_fruits = array_flip($fruits); print_r($flip_fruits);

Output result:

Array ( [apple] => 0 [banana] => 1 [orange] => 2 [lemon] => 3 )

As mentioned above, when using the array_flip() function to reverse the array, the keys and values of the array will be exchanged. Convenient for array reversal operations. However, we can solve this problem through eccentric techniques. You can first use the array_flip() function to interchange the keys and values of the array, then reverse the array, and then use the array_flip() function to restore the original correspondence between keys and values.

Sample code:

$fruits = array( "apple", "banana", "orange", "lemon" ); $flip_fruits = array_flip($fruits); $reverse_flip_fruits = array_reverse($flip_fruits, true); $reverse_fruits = array_flip($reverse_flip_fruits); print_r($reverse_fruits);

The output result is the same as the array_reverse() function sample code, which is:

Array ( [0] => lemon [1] => orange [2] => banana [3] => apple )

The above are two methods of reversing an array in PHP: array_reverse () and array_flip() functions. It should be noted that the array reversed using these functions is reversed based on the order of the index values of the original array. If the order of the original array has been disrupted, the reversed result will also be affected.

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