How to query the intersection of two arrays in php

During the development process using PHP, it is often necessary to operate on arrays. One of the common operations is to query the intersection of two arrays. For example, if we have two student lists, one for class A and one for class B, we may need to query the list of students in both classes.

In PHP, querying the intersection of two arrays is very simple and can be achieved using the array_intersect() function. This function accepts two or more arrays as arguments and returns a new array containing all values ​​that occur simultaneously in the input arrays. The following is an example:

$studentsA = array("Alice", "Bob", "Charlie", "David");
$studentsB = array("Charlie", "David", "Eve", "Frank");
$commonStudents = array_intersect($studentsA, $studentsB);
print_r($commonStudents);

Run the above code, the output is as follows:

Array (
  [2] => Charlie
  [3] => David
)

In the above code, we created two student lists, namely students in class A and class B List. We use the array_intersect() function to get the intersection of these two arrays and store the result in the $commonStudents variable. Finally, we use the print_r() function to print the contents of the $commonStudents variable.

As mentioned above, the array_intersect() function accepts two or more arrays as parameters. If we need to query the intersection of multiple arrays, we just need to add more arrays to the function call. For example:

$studentsA = array("Alice", "Bob", "Charlie", "David");
$studentsB = array("Charlie", "David", "Eve", "Frank");
$studentsC = array("Alice", "Eve", "Grace", "Helen");
$commonStudents = array_intersect($studentsA, $studentsB, $studentsC);
print_r($commonStudents);

Run the above code, the output result is as follows:

Array (
    [0] => Alice
)

In the above code, we created three student lists, which are the student lists of classes A, B and C. We use the array_intersect() function to get the intersection of these three arrays and store the result in the $commonStudents variable. Finally, we use the print_r() function to print the contents of the $commonStudents variable.

One thing to note when using the array_intersect() function is that this function only compares the values ​​of the array, not the keys. In other words, if two arrays have the same value but different keys, the array_intersect() function will also treat them as different elements. If we need to compare two arrays by key, we can use the array_intersect_key() function.

The above describes how to query the intersection of two arrays in PHP, and also introduces how to query the intersection of multiple arrays. Using these functions can help us operate arrays more conveniently, thus improving our development efficiency.

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