How to remove duplicate elements from php array (three methods)

PHP is a widely used server-side scripting language with powerful functions and flexible features, making it the preferred language for back-end development of many websites. In PHP, sometimes you need to remove duplicate elements from an array. This article will introduce how to use various features of PHP to remove duplicate array elements.

Method 1: Use the array_unique() function
PHP’s built-in array_unique() function can remove duplicate values ​​​​in the array. This function will return a new array in which all duplicate values ​​​​are removed. The basic syntax of this function is as follows:

array array_unique(array $array [, int $sort_flags = SORT_STRING ])

Among them, $array is the array that needs to be deduplicated, and $sort_flags is the sorting flag. , used to specify the sorting method of deduplication results, which can be the following values:

• SORT_REGULAR - Compare data types and values ​​
• SORT_NUMERIC - Compare only values, sort in numerical order
• SORT_STRING - compare values ​​only, sort in string order

The sample code is as follows:

<?php   
   $arr = array("a" => "apple", "b" => "banana", "c" => "apple");  
   $result = array_unique($arr);  
   print_r($result); 
?>

The output result is:

Array ( [a] => apple [b] => banana )

above In the example, since the $arr array contains two identical values ​​"apple", after using the array_unique() function to remove duplicates, only one "apple" remains in the result.

Method 2: Use loop traversal
When you need to remove duplicate values ​​in the array, you can also use loop traversal to achieve this. The basic idea is to loop through the array, compare each element with the previous element, and if it is the same as the previous element, delete the element until there are no more duplicate elements in the array.

The sample code is as follows:

<?php   
   $arr = array("a" => "apple", "b" => "banana", "c" => "apple");  
   $newArr = array();  
   foreach ($arr as $value) {  
      if(!in_array($value, $newArr)){  
         $newArr[] = $value;  
      }  
   }  
   print_r($newArr);  
?>

The output result is:

Array ( [0] => apple [1] => banana )

In the above example, a foreach loop is used to traverse the $arr array and store each element in the new In the array $newArr, if it is found that the same value is already contained in $newArr, the value is skipped and the next element is checked.

Method 3: Use array_flip() and array_keys() functions
You can also use PHP’s built-in functions array_flip() and array_keys() to remove duplicates.

The array_flip() function can be used to exchange the keys and corresponding values ​​in the array to achieve the purpose of deduplication. The basic syntax of this function is as follows:

array array_flip(array $array)

Among them, $array is the array whose key values ​​need to be exchanged.

array_keys() function can return all keys in the array. The basic syntax is as follows:

array array_keys(array $array [, mixed $search_value = null [, bool $strict = false ]] )

Among them, $array is the specified array, $search_value is an optional parameter, used to specify the value to be found, if not specified, all keys will be returned, $strict is an optional parameter, used to specify Whether to use congruent comparisons.

The sample code is as follows:

<?php  
   $arr = array("a" => "apple", "b" => "banana", "c" => "apple");  
   $newArr = array_flip(array_keys($arr));  
   print_r($newArr); 
?>

The output result is:

Array ( [apple] => c [banana] => b )

In the above example, first use the array_keys() function to return all the keys in the $arr array, and then use array_flip The () function exchanges keys and values ​​to obtain a new array $newArr. Since the keys in the array must be unique, this method can achieve the effect of deduplication.

Summary
This article introduces three methods of deduplicating array elements in PHP: using the array_unique() function, using loop traversal, and using the array_flip() and array_keys() functions. Different methods have different applicable scenarios and effects, and it is necessary to choose the appropriate method according to the specific situation.

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