How to remove duplicate elements from an array in php

Array is one of the most commonly used data types in PHP. However, sometimes we need to remove duplicate elements from an array. This article will introduce you how to delete duplicate elements from an array using PHP language.

1. Use PHP’s array_unique function

PHP provides a built-in function array_unique, which is used to delete all duplicate elements in the array. Using this function is very simple, just pass an array to the function.

The following is an example:

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

The output result of the above example is:

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

2. Use a loop to delete duplicate elements in the array

Another alternative The method is to remove duplicate elements from the array through a loop. This method takes into account each element in the array and removes it if it already appears in the array. Although this method is more cumbersome, it can handle arrays more flexibly.

The following is an example:

$array = array(1,2,2,3,3,3,4,4,4,4);

for($i=0; $i<count($array); $i++){
  for($j=$i+1; $j<count($array); $j++){
    if($array[$i] == $array[$j]){
      array_splice($array,$j,1);
      $j--;
    }
  }
}
print_r($array);

The output result of the above example is the same as the first method:

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

3. Use PHP’s array_count_values ​​function

Also There is a way to remove duplicate elements from an array, which uses PHP's array_count_values ​​function. This function returns an associative array, the key is the unique element in the array, and the key value is the number of times the element appears in the array.

Therefore, we can pass the array to the array_count_values ​​function, then use the array_keys function to extract the unique key names, and finally return a new array.

The following is an example:

$array = array(1,2,2,3,3,3,4,4,4,4);

$count_array = array_count_values($array);
$new_array = array_keys($count_array);

print_r($new_array);

The output result of the above example is the same as the first method:

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

Summary

All three methods above can be used For removing duplicate elements from an array, the specific method you choose depends on your specific needs. Here, we introduced using PHP’s array_unique function, using a loop to remove duplicate elements in an array, and using PHP’s array_count_values ​​function. These methods are three simple and effective ways to remove duplicate elements from an array in PHP.

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