Detailed explanation of how to use array_diff_key() of PHP array function

As a popular programming language, PHP’s array functions are also very powerful. When you need to compare the key names of two arrays, you can use the array_diff_key() function. This function can help us find out the key names that are in the first array but do not exist in the second array, and compare the differences between the arrays. This article will introduce in detail how to use the array_diff_key() function.

Basic usage of the array_diff_key() function

The syntax of the array_diff_key() function is:

array array_diff_key ( array $array1 , array $array2 [, array $... ] )

This function receives multiple arrays as parameters, where the first parameter is the original Array, the subsequent parameters are the arrays to be compared. This function returns a new array corresponding to keys that exist in the first array but do not exist in other arrays.

For example, we have two arrays:

$array1 = array('name' => 'Peter', 'age' => 20, 'address' => 'Shanghai');
$array2 = array('name' => 'Mike', 'sex' => 'male', 'address' => 'Beijing');

We can compare these two arrays through the following code:

$result = array_diff_key($array1, $array2);
print_r($result);

The output result is as follows:

Array ( [age] => 20 )

As can be seen from the results, we got a new array that only contains elements with the key name 'age'. This is because 'age' only exists in $array1 and does not exist in $array2.

Notes

It should be noted that the array_diff_key() function only compares the key names of the array, not the key values. Therefore, even if some keys in the two arrays correspond to the same key value, the function will still list them as differences.

The array_diff_key() function also supports comparing differences between multiple arrays. For example, we have three arrays:

$array1 = array('name' => 'Peter', 'age' => 20, 'address' => 'Shanghai');
$array2 = array('name' => 'Mike', 'sex' => 'male', 'address' => 'Beijing');
$array3 = array('name' => 'Lucas', 'age' => 22, 'hobby' => 'swimming');

We can compare these three arrays through the following code:

$result = array_diff_key($array1, $array2, $array3);
print_r($result);

The output results are as follows:

Array ( [age] => 20 )

As can be seen from the results, We get a new array that only contains elements with the key name 'age', because 'age' only exists in $array1 and does not exist in the other two arrays.

Conclusion

The array_diff_key() function is a very useful PHP array function that can help us quickly find the difference between two or more arrays. When using this function, we need to note that it only compares the key names of the array, not the key values.

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