Introduction to how to use the array_flip() function in the PHP function library

In PHP, the array_flip() function is one of the most commonly used functions. This function is used to reverse the keys and values ​​in the array, that is, reverse the key-value pairs in the array, and the returned result is a new array.

The basic syntax of this function is as follows:

array array_flip (array $array)

Parameter description:

• $array is to be reversed Array to rotate.

Return value:

• Returns the reversed array. If the parameter passed in is not a valid array, it returns bool(false).

The following is an example to introduce the use of array_flip():

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

The output results are as follows:

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

In the above example, we first created An array containing three key-value pairs, then using the array_flip() function to reverse its keys and values, and finally output the reversed array.

It should be noted that if there are two or more elements with the same value in the original array, only the last element will be retained in the reversed array, and other identical elements will be overwritten. For example, in the example below, two key-value pairs "a" and "b" have the same value and are reversed so that only the last occurrence of the key-value pair is retained.

$array = array('a' => 'apple', 'b' => 'banana', 'c' => 'banana');
$flippedArray = array_flip($array);
print_r($flippedArray);

The output result is as follows:

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

Finally, it should be noted that when using the array_flip() function, you need to ensure that the value of the original array is unique or can be treated as a unique string key, otherwise the results will not be as expected.

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