php array statistics different values

In PHP development, arrays are a very commonly used data type. We usually use arrays to store a series of data. Sometimes, we need to count different values ​​​​in an array, such as counting the number of times different elements appear in an array. This article will show you how to count different values ​​in an array using PHP.

1. array_count_values ​​function

PHP has a built-in function array_count_values, which can be used to count the number of occurrences of each value in an array. The prototype of this function is as follows:

array_count_values(array $array): array

This function requires an array as a parameter and returns an associative array, where the keys are different values ​​in the original array and the value is the number of times the value appears in the original array. For example:

$array = array(1, 1, 2, 3, 3, 3);
$count = array_count_values($array);
print_r($count);

Output:

Array(
    [1] => 2
    [2] => 1
    [3] => 3
)

The original array here is [1, 1, 2, 3, 3, 3], in the associative array returned by the function, the key 1 appears 2 times in the original array, key 2 appears 1 time in the original array, and key 3 appears 3 times in the original array.

It should be noted that this function is only valid for index arrays and associative arrays. For other types of arrays, an empty array will be returned.

2. Custom function

In addition to using the array_count_values function, we can also write a function ourselves to complete similar functions. The following is an example function:

function array_count_unique(array $array): array
{
    $counts = array();
    foreach ($array as $value) {
        if (isset($counts[$value])) {
            $counts[$value]++;
        } else {
            $counts[$value] = 1;
        }
    }
    return $counts;
}

This function accepts an array and returns an associative array, where the keys are different values ​​in the original array and the value is the number of times the value appears in the original array. The specific implementation idea is to traverse the original array, count the number of occurrences of each value, and then use the value as the key and the number of occurrences as the value to construct the result array.

We can test this function using the following code:

$array = array(1, 1, 2, 3, 3, 3);
$count = array_count_unique($array);
print_r($count);

Output:

Array(
    [1] => 2
    [2] => 1
    [3] => 3
)

Same result as array_count_values function.

It should be noted that this function is only valid for index arrays and associative arrays. For other types of arrays, an empty array will be returned.

3. Performance comparison

Although using PHP's built-in array_count_values function and custom functions can complete the function of counting different values ​​​​in an array, they Performance may vary. We can test the performance of both methods by using the microtime function.

The following is a test example using the array_count_values function:

$array = range(1, 10000);
shuffle($array);
$start = microtime(true);
$count = array_count_values($array);
$end = microtime(true);
echo 'array_count_values: ' . ($end - $start) . ' seconds';

The following is a test example using a custom function:

$array = range(1, 10000);
shuffle($array);
$start = microtime(true);
$count = array_count_unique($array);
$end = microtime(true);
echo 'array_count_unique: ' . ($end - $start) . ' seconds';

Two test examples The input is the same, both are a random array with a length of 10000, and the execution time of each method is output. We can run these two code snippets multiple times and compare the average running time of the two functions.

In the environment I tested, the time difference between the two methods is not obvious. Usually the array_count_unique function is slightly faster than the array_count_values function, but the difference between the two methods is not significant. big. Therefore, in practical applications, the appropriate method can be selected according to needs.

Summary

This article introduces how to use PHP to count different values ​​​​in an array. We can use PHP's built-in array_count_values function, or we can write a function ourselves. Both methods accomplish similar functions, but with slightly different performance. In practical applications, the appropriate method can be selected according to needs.

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