How to find the intersection of arrays in php

Array is a data structure widely used in PHP programming. Intersection operation is a common requirement for operating on arrays. In PHP, we can use a number of different methods to find the intersection of two or more arrays. This article will discuss and introduce this topic in detail.

The first method is to use the array_intersect function to find the intersection of two arrays. This function takes two or more arrays as arguments and returns the intersection of the elements in these arrays. Here is a sample code using the array_intersect function:

$firstArray = array("apple", "orange", "banana", "pear");
$secondArray = array("pear", "watermelon", "grape", "banana");

$result = array_intersect($firstArray, $secondArray);

print_r($result);

The above code will return an array containing "banana" and "pear". Because both elements exist in both $firstArray and $secondArray.

The second method is to use the built-in function array_values ​​to disassemble the values ​​in the intersection array. The decomposed value is still an array, which only contains the values ​​of the intersection part. The following is a sample code using the array_values ​​function:

$firstArray = array("apple", "orange", "banana", "pear");
$secondArray = array("pear", "watermelon", "grape", "banana");

$result = array_intersect($firstArray, $secondArray);

$result = array_values($result);

print_r($result);

After running, a new array containing the intersection elements will be returned, namely: "banana" and "pear".

The third method is to use a foreach loop statement to traverse the first array and check whether its elements also exist in the second array. If the element exists in the second array, it is added to the intersection array. Here is sample code using a foreach loop statement:

$firstArray = array("apple", "orange", "banana", "pear");
$secondArray = array("pear", "watermelon", "grape", "banana");

$result = array();

foreach ($firstArray as $value) {
    if (in_array($value, $secondArray)) {
        $result[] = $value;
    }
}

print_r($result);

After running this code will return a new array containing the intersection elements.

The fourth method is to use the array_filter function to filter the intersection of two arrays. This function accepts two parameters, the first parameter is the array to be filtered, and the second parameter is a callback function. The callback function will be used to filter the array, and only elements that meet the criteria will be retained. A sample code using the array_filter function is as follows:

$firstArray = array("apple", "orange", "banana", "pear");
$secondArray = array("pear", "watermelon", "grape", "banana");

$result = array_filter($firstArray, function($item) use ($secondArray) {
    return in_array($item, $secondArray);
});

print_r($result);

After running this code will return a new array containing intersection elements.

To sum up, there are many different methods that can be used to find the intersection of two arrays. The simplest way is to use the array_intersect function, and then use the array_values ​​function on the returned array to break out the intersection parts. Basic intersection operations can also be implemented using the foreach loop statement and the in_array function. Finally, the array_filter function provides a more advanced method that can use callback functions to implement intersection operations and can adjust the intersection calculation rules more flexibly.

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