Analyze the role of PHP function array_flip() in deleting duplicate array elements_PHP tutorial

We all know that there are many ways to delete array elements in PHP. The commonly used function is array_unique() in PHP. Then the PHP function array_flip() we introduce to you today is about 5 times more efficient than the array_unique() function in deleting duplicate elements from an array.
PHP function array_flip() format:

Copy code The code is as follows:

array array_flip ( array trans )
//array_flip -- Swap the keys and values ​​in the array

array array_flip ( array trans ) //array_flip -- Swap the keys and values ​​in the array
method As follows:

Copy code The code is as follows:

$arr = array(…………);//Suppose there is a An array of 10,000 elements contains duplicate elements.
$arr = array_flip(array_flip($arr)); //This way duplicate elements can be deleted.

What on earth is going on? Let’s take a look at the function of array_flip(): The PHP function array_flip() is used to exchange the key and value of each element of an array, such as:

Copy code The code is as follows:

$arr1 = array ("age" => 30, "name" => "Script Home");
$arr2 = array_flip($arr1) ; //$arr2 is array(30 => "age", "Script Home" => "name");

In the PHP array, different elements are allowed to be taken The same value, but the same key name is not allowed to be used by different elements, such as:

Copy code The code is as follows:

$arr1 = array ("age" => 30, "name" => "Script Home", "age" => 20); "age" => 20 will replace "age" => ; 30 
$arr1 = array ("name" => "Script Home", "age" => 20);

Here $arr1 and $arr2 are equal.
So, we can know why array_flip(array_flip($arr)) can delete duplicate elements in the array. First, the value in $arr will become a key name, because the value is repeated. After becoming a key name, these repeated values ​​will become duplicate key names. The PHP engine will delete the duplicate key names and only keep the last one. . For example:

Copy code The code is as follows:

$arr1 = array ("age" => 30, "name" => "Script Home", "age" => 20);
$arr1 = array_flip($arr1); //$arr1 becomes array("Script Home" => "name" , 20 => "age");
//Restore the key name and value of $arr1:
$arr1 = array_flip($arr1);

The above PHP The code of the function array_flip() is written more concisely:

Copy the code The code is as follows:

$arr1 = array_flip(array_flip ($arr1));

http://www.bkjia.com/PHPjc/327873.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/327873.htmlTechArticleWe all know that there are many ways to delete array elements in PHP, and the commonly used functions are php in array_unique(). So the PHP function array_flip() we introduce to you today is...