How to remove unique values ​​from php array

PHP is a very popular dynamic programming language that is widely used in web development. During the development process, we often need to process data, and arrays are a very common data structure. When we need to remove unique values ​​from an array, we can use the following method:

Method 1: Use the array_unique function to remove duplicates

The array_unique function is one of the commonly used functions in PHP. Can remove duplicate values ​​from an array. This function returns an array with no duplicate values. The usage method is as follows:

<?php
    $arr = array(1, 1, 2, 2, 3, 4, 4, 5);
    $unique_arr = array_unique($arr);
    print_r($unique_arr);
?>

The output result is: Array ( [0] => 1 [2] => 2 [4] => 3 [5] => 4 [6] => ; 5)

Method 2: Use foreach loop to remove duplicates

When we don’t want to use the array_unique function, we can also use foreach loop to remove duplicates. The specific steps are as follows:

1. Create a new empty array $result to store the results after deduplication.
2. Use foreach loop to traverse the original array $arr.
3. Determine whether each value in the original array exists in the new array $result. If it does not exist, add it to $result.

Code example:

<?php
    $arr = array(1, 1, 2, 2, 3, 4, 4, 5);
    $result = array();
    foreach($arr as $a){
        if(!in_array($a, $result)){
            $result[] = $a;
        }
    }
    print_r($result);
?>

The output result is: Array ( [0] => 1 [1] => 2 [2] => 3 [3] = > 4 [4] => 5 )

Method 3: Use the array_flip function to remove duplicates

The array_flip function can exchange the keys and values ​​​​in the array and use it as the value of the new array keys to remove duplicates. The usage method is as follows:

<?php
    $arr = array(1, 1, 2, 2, 3, 4, 4, 5);
    $unique_arr = array_flip(array_flip($arr));
    print_r($unique_arr);
?>

The output result is: Array ( [0] => 1 [2] => 2 [4] => 3 [5] => 4 [6] => ; 5)

Summary:

The above are several ways to remove unique values ​​from an array in PHP. Either way, the same functionality can be achieved. In actual development, choosing the appropriate method based on requirements and performance is the most important.

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