How to remove duplicate elements from array in PHP

As websites and applications become more complex, arrays are used more frequently and in greater quantities. However, when processing large amounts of data, duplicate elements sometimes appear, which reduces the performance of the program and wastes time and resources. Therefore, deleting identical array members has become a task that PHP programmers often need to deal with.

This article will introduce how to remove duplicate elements from an array in PHP, providing useful practical tips and examples for those reading this article.

1. Use the array_unique() function to delete the same elements in the array

In PHP, the most basic way to delete duplicate elements is to use the array_unique() function. This function removes all duplicates from the array, keeping only the first occurrence, and returns a new array containing only the unique element.

Code example:

$array = array(1, 2, 2, 3, 3, 3, 4, 5, 5);
$new_array = array_unique($array) ;
print_r($new_array);

Output:

Array
(
[0] => 1
[1] => 2
[3] => 3
[6] => 4
[7] => 5
)

2. Use foreach loop to delete the same elements in the array

In addition to the array_unique() function, PHP has other methods to delete identical array members. Among them, using a foreach loop can handle arrays more flexibly and delete duplicate elements when they are encountered.

Code example:

$array = array(1, 2, 2, 3, 3, 3, 4, 5, 5);
$new_array = array();

foreach($array as $value){
if(!in_array($value, $new_array)) {

$new_array[] = $value;

}
}

print_r( $new_array);

Output:

Array
(
[0] => 1
[1] => 2
[3] = > 3
[6] => 4
[7] => 5
)

The above code uses a foreach loop to traverse the array. During each iteration, it first checks if the current value exists in the array. If it does not exist, the element is added to the new array. Otherwise, the element is skipped and the loop continues.

3. Use the array_count_values() function to delete the same elements in the array

PHP also provides another useful function that can help delete the same elements in the array. This function is array_count_values(), which returns a new array containing the number of occurrences of each array element.

Code example:

$array = array(1, 2, 2, 3, 3, 3, 4, 5, 5);
$count_array = array_count_values($array) ;
$new_array = array();

foreach($count_array as $key => $value){
$new_array[] = $key;
}

print_r($new_array);

Output:

Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
)

The above code first uses the array_count_values() function to calculate each value in the array. number of occurrences of elements, then use a foreach loop to iterate through the new array and add each key to the new array.

4. Use the array_flip() function to delete the same elements in the array

Another useful PHP function is array_flip(), which can swap the key values ​​​​in the array. This means that the values ​​in the array will become the keys in the new array, and the keys in the original array will become the values ​​in the new array. By using this function, you can easily delete the same elements in the array.

Code example:

$array = array(1, 2, 2, 3, 3, 3, 4, 5, 5);
$new_array = array_flip($array) ;
$new_array = array_flip($new_array);
print_r($new_array);

Output:

Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
)

The above code first uses the array_flip() function to swap the key values ​​​​in the original array, so that the keys of the same element will be converted into values. Next, use array_flip() again to exchange the values ​​and keys in the array back and turn them into keys again. This completes the task of deleting the same elements.

Conclusion

In PHP programming, processing arrays is a frequently used task. And among these tasks, deleting the same elements in an array is a frequently encountered task. This article introduces four implementation methods based on the array_unique() function, foreach loop, array_count_values() function and array_flip() function, which can help readers better complete this task. Readers can choose one of the methods, or a combination of methods according to the actual needs of the task, to achieve a more elegant and efficient program effect.

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