PHP's array_diff() function: How to compare two arrays and return the difference value

PHP's array_diff() function: How to compare two arrays and return the difference value, specific code examples are needed

In the PHP language, arrays are the most common data A structure often used to store a set of data or records. When you need to compare the differences between two arrays, PHP provides a convenient function array_diff(), which compares two arrays and returns all different values.

The syntax of the array_diff() function is as follows:

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

This function accepts two or multiple arrays as arguments, returns a new array containing all distinct values. It works by comparing the values ​​in the first array with the values ​​in the following arrays and returning the values ​​in the first array that are different from the remaining arrays. If a value is the same in all arrays, it will not be returned.

Next we will demonstrate the usage of the array_diff() function through a simple example.

First, let’s define two arrays:

$array1 = array("foo", "bar", "baz");
$array2 = array("bar", "qux");

Of these two arrays, $array1 contains three different strings, while $array2 contains two different strings. where "bar" is the value they share.

Next, we will use the array_diff() function to compare the two arrays and return all the different values:

$diff = array_diff($array1, $array2);
print_r($diff);

The output of the above code is:

Array
(
    [0] => foo
    [2] => baz
)

As you can see, the $diff array contains all values ​​in $array1 that are different from $array2. The value "bar", which exists in both arrays, is not returned.

We can also compare values ​​in multiple arrays by using more array parameters:

$array3 = array("qux", "corge");
$diff = array_diff($array1, $array2, $array3);
print_r($diff);

The above code combines $array1 with $array2 and $array3 to return all differences The value, the output result is:

Array
(
    [0] => foo
    [2] => baz
)

It can be seen that "qux" appearing in the third array is not returned because it also exists in $array2.

In addition, if you need to compare associative arrays, you can use the array_diff_assoc() function. Its usage is similar to array_diff(), but it will also compare the key values ​​in the array.

Finally, it should be noted that the array_diff() function only compares values, not keys. For example, although the following two arrays have the same values, but different key values:

$array1 = array("foo" => 1, "bar" => 2, "baz" => 3);
$array2 = array("qux" => 1, "quux" => 2, "baz" => 3);

When using array_diff() to compare these two arrays, only their values ​​will be compared, not the key values. . Therefore, $array1 and $array2 will be considered different arrays.

To sum up, the array_diff() function is a very convenient array processing function in PHP. It can compare different values ​​between multiple arrays and return a new array. Using this function can help us process arrays more conveniently.

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