How to remove unique elements from a php array

In the process of Web development, PHP language has become one of the most popular programming languages. Among them, the array in PHP is a very common data structure. It is very flexible and adaptable and can be used to store and process various types of data.

However, in development, we often encounter the need to remove unique elements from a very large array. For this problem, PHP arrays provide many different solutions. Let’s introduce them one by one below.

Method 1: Use the array_unique function

The array_unique function is a function that comes with PHP and is used to remove duplicate elements from an array and return an array of non-duplicate elements. Its usage is very simple, as shown below:

$my_array = array(1,2,2,3,3,3,4,4,4,4);
$unique_array = array_unique($my_array);
print_r($unique_array);

The above code will output the following results:

Array
(
    [0] => 1
    [1] => 2
    [3] => 3
    [6] => 4
)

As you can see, through the array_unique function, we can easily remove unique items from the original array element.

Method 2: Use array_flip and array_keys functions

If we need to return an array of key names with non-repeating elements, we can use a combination of array_flip and array_keys functions, as shown below:

$my_array = array(1,2,2,3,3,3,4,4,4,4);
 $unique_keys = array_keys(array_flip($my_array));
 print_r($unique_keys);

The above code will output the following results:

Array
(
    [0] => 0
    [1] => 1
    [2] => 3
    [3] => 6
)

As you can see, through the array_flip and array_keys functions, we get an array of unique element key names.

Method 3: Use loops and in_array function

This is a relatively common approach. We can use a loop to traverse the entire array, and then use the in_array function to check whether the current element already exists in the array. Determine the non-repeating element array. If it does not exist, add it to the non-repeating element array, as shown below:

$my_array = array(1,2,2,3,3,3,4,4,4,4);
$unique_array = array();
foreach($my_array as $value){
    if(!in_array($value,$unique_array)){
        $unique_array[] = $value;
    }
}
print_r($unique_array);

The above code will output the following result:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
)

Here we Through the combination of loop and in_array function, unique elements are successfully removed from the original array.

Method 4: Use the array_reduce function

The array_reduce function can be used to iterate over an array and reduce each value in the array to a single value. Therefore, if we want to get an array with non-repeating elements, we can use the array_reduce function to operate. The code is as follows:

$my_array = array(1,2,2,3,3,3,4,4,4,4);
$unique_array = array_reduce($my_array,function($result,$value){
    if(!in_array($value,$result)){
        $result[] = $value;
    }
    return $result;
}, array());
print_r($unique_array);

The above code will output the following results:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
)

Okay We see that we have achieved the purpose of removing non-repeating elements from the original array by using the combination of array_reduce and in_array functions.

Summary

The above are several methods for removing non-repeating elements from PHP arrays. Although each method has its characteristics and uses, it should be noted that when processing large arrays, the efficiency of each method may be different, and you need to choose and use it according to the situation.

I hope this article will help everyone understand and use PHP arrays.

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