PHP function library analysis: array_unique()

In PHP programs, the ease of use and performance of the program can be greatly increased by using function libraries. Among them, the array_unique() function is one of them. This article will introduce the array_unique() function in detail from the following aspects:

1. Function definition and parameters

The definition of the array_unique() function is to remove duplicates in the array value and returns a new array. The syntax of the function is as follows:

array_unique(array $array[, int $sort_flags = SORT_STRING]):array

Among them, the $array parameter is required and represents the array to be deduplicated. The $sort_flags parameter is optional and indicates the sorting method. The default value is SORT_STRING, which sorts the elements after coercing them to strings.

2. Function implementation

array_unique() function implementation is very simple. The basic idea is to create a new empty array $result, then iterate through each element in the $array array, and if the element is not in the $result array, add the element to the $result array. Finally, the $result array is returned. The following is the code implementation of the function:

function array_unique(array $array, int $sort_flags = SORT_STRING): array
{
    $result = array();
    foreach ($array as $value) {
        if (!in_array($value, $result)) {
            $result[] = $value;
        }
    }
    if ($sort_flags !== null) {
        sort($result, $sort_flags);
    }
    return $result;
}

3. Example of function usage

The following is the example code of using array_unique() function to remove duplicates:

$array = array("red", "green", "blue", "green");
$new_array = array_unique($array);
print_r($new_array);

Output The result is:

Array
(
    [0] => red
    [1] => green
    [2] => blue
)

4. Performance optimization

In actual use, in order to improve the performance of the program, we can use PHP's built-in array_flip() function to optimize array_unique() Function implementation. The array_flip() function swaps the keys and values ​​in the array, so the deduplicated array becomes an array with non-duplicate keys. Then use the array_keys() function to get the keys of the array to get the deduplicated array. The following is the optimized code implementation:

function array_unique(array $array, int $sort_flags = SORT_STRING): array
{
    $tmp_array = array_flip($array);
    if ($sort_flags !== null) {
        ksort($tmp_array, $sort_flags);
    }
    return array_keys($tmp_array);
}

5. Summary

array_unique() function is a very practical PHP function that plays an important role in deduplication. Through the introduction of this article, we can have a deeper understanding of the parameters, implementation and performance optimization of this function. At the same time, in actual use, we can also perform some optimizations on this function based on the actual situation and performance requirements to improve the performance and efficiency of the program.

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