PHP function library exploration: array_reverse()

As a widely used server-side scripting language, PHP has a powerful function library that can easily complete various programming tasks. Among them, the array_reverse() function is one of the more commonly used functions in PHP. This article will explore this function and introduce its usage and related features.

1. What is the array_reverse() function?

array_reverse() function is an array function in PHP, used to reverse the order of elements in an array. This function can handle index arrays and associative arrays, and returns a new array without changing the key-value pairs of the original array.

2. Function syntax and parameters

The basic syntax of the array_reverse() function is as follows:

array array_reverse(array $array [, bool $preserve_keys = FALSE ]);

Parameter description:

• $array: Required, specifies the array to reverse.
• $preserve_keys: Optional, indicating whether to retain the key names of the original array. Its default value is FALSE. If set to TRUE, the key names in the reversed new array will be the same as the original array.

3. How to use the function

Using the array_reverse() function is very simple, just pass in the array to be reversed as a parameter. The following are some examples of array reversal:

① Index array reversal:

$numbers = array(1, 2, 3, 4, 5);
$rev_numbers = array_reverse($numbers);
print_r($rev_numbers); // 输出：Array ( [0] => 5 [1] => 4 [2] => 3 [3] => 2 [4] => 1 )

② Associative array reversal:

$infos = array('name' => 'Tom', 'age' => 20, 'sex' => 'male');
$rev_infos = array_reverse($infos);
print_r($rev_infos); // 输出：Array ( [sex] => male [age] => 20 [name] => Tom )

③ Retain the original array key name:

$fruits = array('a' => 'apple', 'b' => 'banana', 'c' => 'cherry');
$rev_fruits = array_reverse($fruits, true);
print_r($rev_fruits); // 输出：Array ( [c] => cherry [b] => banana [a] => apple )

4. Function return value

array_reverse() function will return a new array containing the reverse order of all elements in the original array. If the original array is an empty array, an empty array is returned. If the preserve_keys parameter is TRUE, the key names of the returned new array are the same as the original array.

5. Notes

You need to pay attention to the following issues when using the array_reverse() function:

• The array_reverse() function is only used to operate arrays , cannot be used for other data types.
• If the preserve_keys parameter is TRUE, the key names of the original array will be retained, but the data type of each key name may change. For example, if the key name of the original array is an integer type, the corresponding key name of the reversed new array will become a string type.
• If the original array is an empty array, the reversed result is still an empty array.

6. Summary

array_reverse() function is one of the most practical array functions in PHP. It can easily reverse the order of elements in an array and Return a new array. When writing PHP programs, rational use of this function can improve the efficiency of the code and make the program more concise and practical.

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