How to find intersection of php arrays

With the development of the Internet, the development of various websites and applications has increasingly become one of the main tasks of programmers. In this process, array operations are a very common operation. As an excellent website development language, PHP's array operation function is also very powerful and flexible.

This article mainly introduces the related usage methods of PHP array intersection, hoping to bring help to readers.

1. What is an array

Before introducing the intersection of arrays, let’s briefly introduce what an array is.

Array is a common data type that represents a set of ordered values ​​(elements). Each element has an index value through which the corresponding element value can be accessed. Arrays in PHP can be viewed as hash tables or maps, which require a key to access the subscript of an element.

The definition form of array is: $array = array('value1', 'value2', ..., 'valueN');

Among them, value1, value2, ..., valueN means The value of the array element. Elements in an array can be accessed using keys of type integer or string, for example: $array[0], $array['foo'] .

2. How to find the intersection of two arrays

To find the intersection of two arrays, the easy-to-understand way is to find the elements that exist in both arrays. There are several ways to accomplish this in PHP.

1. array_intersect

array_intersect() function is used to calculate the intersection of arrays and returns an array that contains values ​​that appear in multiple parameter arrays at the same time. The returned The order of the array elements is the same as the order of the first parameter array.

For example:

$arr1 = array(1, 2, 3, 4);
$arr2 = array(3, 4, 5, 6);
$result = array_intersect($arr1, $arr2);
print_r($result);
// 输出结果为 Array ( [2] => 3 [3] => 4 )

2. array_intersect_assoc

array_intersect_assoc() function is used to calculate the intersection of arrays (compare key names and key values). The function returns a An array that contains key names and key values ​​that appear in multiple parameter arrays at the same time. The order of the returned array elements is the same as the order of the first parameter array.

For example:

$arr1 = array("a" => "red", "b" => "green", "c" => "blue");
$arr2 = array("a" => "red", "b" => "blue", "c" => "green");
$result = array_intersect_assoc($arr1, $arr2);
print_r($result);
// 输出结果为 Array ( [a] => red )

3. array_uintersect

array_uintersect() function is used to calculate the intersection of arrays and compare array values ​​using a user-defined callback function. This function returns an array containing the values ​​that appear in multiple argument arrays simultaneously, with the returned array elements in the same order as the first argument array.

For example:

function myfunction($a, $b)
{
    if ($a === $b)
    {
        return 0;
    }
    return ($a > $b) ? 1 : -1;
}
$arr1 = array("a" => "red", "b" => "green", "c" => "blue");
$arr2 = array("a" => "red", "b" => "blue", "c" => "green");
$result = array_uintersect($arr1, $arr2, "myfunction");
print_r($result);
// 输出结果为 Array ( [a] => red )

When using these functions, you need to note that the array parameter passed in must be a real array type. If it is not an array type, the function will throw an E_WARNING mistake.

3. Summary

Through the introduction of this article, we can see that it is very easy to find the intersection of two arrays in PHP. You only need to use the relevant functions provided by PHP to easily implement the intersection operation of arrays. In practical applications, these methods can be applied flexibly to improve the efficiency and readability of the program.

If readers want to learn more about PHP array operations, they can refer to the array-related chapters in the PHP official documentation.

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