PHP custom implementation of array intersection

In PHP development, array intersection is a common operation. However, the array intersection function provided by PHP can only handle the case of two arrays. When we need to process the intersection of multiple arrays, we need to customize the intersection operation.

This article will introduce how to customize the intersection of PHP arrays and provide the implementation code.

1. Problem Description

We need to process the intersection of multiple arrays. For example, there are the following four arrays:

$arr1 = array(1, 2, 3);
$arr2 = array(2, 3, 4);
$arr3 = array(3, 4, 5);
$arr4 = array(4, 5, 6);

Now we need to solve these four Intersection of arrays.

2. Solution

We can achieve array intersection through the following steps:

2.1 Store the elements of all arrays into a new array, and then Perform a deduplication operation on the new array.

2.2 Count the number of times each element appears in the original array. If the number is equal to the number of original arrays, it means that the element has appeared in all original arrays, and it will be added to the result array.

The following is the specific implementation code:

function array_intersect_multi() {
  $arrays = func_get_args();
  $counts = array_count_values(call_user_func_array('array_merge', $arrays));
  $intersected_array = array();
  $arrays_count = count($arrays);
  
  foreach ($counts as $value => $count) {
    if ($count === $arrays_count) {
      $intersected_array[] = $value;
    }
  }

  return $intersected_array;
}

3. Function description

The function array_intersect_multi() in the above code can implement multiple Array intersection operation.

This function has one input parameter, which is an array collection. An array collection is an array composed of multiple arrays.

This function will add the elements of all arrays in the array collection to the new array and perform a deduplication operation on the new array.

Then, the function will count the number of times each element appears in the original array. If the number is equal to the number of the original array, it means that the element has appeared in all the original arrays, and it will be added to the result array.

Finally, the function will return the array intersection result.

4. Example

We can use the above function to solve the intersection of four arrays. The example is as follows:

$arr1 = array(1, 2, 3);
$arr2 = array(2, 3, 4);
$arr3 = array(3, 4, 5);
$arr4 = array(4, 5, 6);

$intersected_array = array_intersect_multi($arr1, $arr2, $arr3, $arr4);
print_r($intersected_array);

The output result is:

Array
(
    [0] => 4
)

As you can see, the intersection of the four arrays is 4.

5. Summary

By customizing the array intersection operation, we can easily handle the intersection of multiple arrays. This article introduces the steps and code to implement array intersection. I hope it will be helpful to everyone.

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