Use PHP array_diff() function to calculate the difference set

In PHP programming, we often need to compare the differences between two arrays. In this case, we can use PHP's array_diff() function to calculate the difference between the two arrays. The difference set is the set of elements that exist in the first array but do not exist in the second array.

The array_diff() function accepts two or more arrays as parameters and returns a difference array based on the elements in the first array. The following is the basic syntax of the function:

array_diff(array1, array2, array3, ...)

Among them, array1 is a required parameter, while array2 and subsequent arrays are optional parameters. This function will compare the elements in array1 with the elements of other arrays and return a collection of elements that exist only in array1 but not in other arrays.

Below we can use a practical case to illustrate how to use the array_diff() function to calculate the difference set:

<?php
$arr1 = array('apple', 'banana', 'orange', 'pear');
$arr2 = array('banana', 'pear');

$diff = array_diff($arr1, $arr2);

print_r($diff);
?>

In the above code, we created two arrays $arr1 and $arr2, Among them, $arr1 contains the names of all fruits, while $arr2 only contains part of the names. Then we call the array_diff() function to compare the two arrays, calculate the difference, and finally return the fruit names that only exist in $arr1.

After running this code, we will get the following output:

Array
(
    [0] => apple
    [2] => orange
)

As you can see, the output result is an array, including all $array1 elements that do not exist in $arr2, also Just 'apple' and 'orange'.

It is worth noting that the array_diff() function will only compare the values ​​​​in the array, without considering their key names. If we need to compare key-value pairs, we can use the array_diff_assoc() function. At the same time, if we need to compare the differences between multiple arrays, we can pass in multiple arrays as function parameters.

In general, using PHP's array_diff() function can easily calculate the difference between two or more arrays, and the code is also quite simple and easy to understand.

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