php array_flip() and array_uniqure() remove duplicate elements from array_PHP tutorial

There are several functions to delete duplicate elements from an array in PHP. One is array_unique() and the other is array_flip() and array_uniqure() functions, but the latter is several times more performant than the former, so I will only introduce the two. to remove duplicate array elements.

The method is as follows:

The code is as follows

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代码如下 复制代码 $arr = array(…………) ;// 假设有数组包含一万个元素，里面有重复的元素。   $arr = array_flip(array_flip($arr)); // 这样便可以删除重复元素。 $arr = array(…………) ;// Suppose there is an array containing ten thousand elements, with duplicate elements in it. $arr = array_flip(array_flip($arr)); // This will remove duplicate elements.  代码如下 复制代码   $arr1 = array("age" => 30, "name" => '快乐园');   $arr2 = array_flip($arr1);　// $arr2 就是 array(30 => "age", '快乐园' => "name");

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

The code is as follows	Copy code
代码如下 复制代码   $arr1 = array("age" => 30, "name" => '快乐园', "age" => 20);　"age" => 2 0将会取代 "age" => 30   $arr1 = array("name" => '快乐园', "age" => 45); $arr1 = array("age" => 30, "name" => 'Happy Garden'); $arr2 = array_flip($arr1); // $arr2 is array(30 => "age", 'Happy Garden' => "name");

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

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代码如下 复制代码 $arr1 = array("age" => 30, "name" => '快乐园', "age" => 20);   $arr1 = array_flip($arr1); // $arr1 变成了 array("快乐园" => "name", 20 => "age");   // 再把 $arr1 的键名与值还复：   $arr1 = array_flip($arr1); $arr1 = array("age" => 30, "name" => 'Happy Garden', "age" => 20); "age" => 2 0 will replace "age" => 30 $arr1 = array("name" => 'Happy Garden', "age" => 45);

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. . Such as:

代码如下	复制代码
function delmember(&$array, $id) { $size = count($array); for($i = 0; $i <$size - $id - 1; $i ++) { $array[$id + $i] = $array[$id + $i + 1]; } unset($array[$size - 1]); }

<🎜> <🎜>

The code is as follows	Copy code
<🎜>$arr1 = array("age" => 30, "name" => 'Happy Garden', "age" => 20); $arr1 = array_flip($arr1); // $arr1 becomes array("Happy Garden" => "name", 20 => "age"); //Restore the key name and value of $arr1: $arr1 = array_flip($arr1);

The above code can be written more concisely: $arr1 = array_flip(array_flip($arr1)); Some custom functions //Function to delete duplicate elements in an array

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function delmember(&$array, $id) { $size = count($array); for($i = 0; $i <$size - $id - 1; $i ++) <🎜> { <🎜> $array[$id + $i] = $array[$id + $i + 1]; <🎜> } <🎜> unset($array[$size - 1]); <🎜> } <🎜>

//使用例子：

代码如下 代码如下 复制代码 $output = array(1, 2, 2, 'www.bKjia.c0m', 5, 4, 4, 4, 2, 7, 5, 9, 10); delsame($output); while(list($key, $value) = each($output)) { echo "$key:$value"." "; } //方法二 function uniquearray($array) { // get unique elts as keys in assoc. array for ($i=0,$n=count($array, 1);$i<$n;$i ) $u_array[$array[$i]] = 1; // copy keys only into another array reset($u_array, 1); for ($i=0,$n=count($u_array, 1);$i<$n;$i ) { $unduplicated_array[] = key($u_array, 1); next($u_array, 1); } return $unduplicated_array; }

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$output = array(1, 2, 2, 'www.bKjia.c0m', 5, 4, 4, 4, 2, 7, 5, 9, 10);
delsame($output);
while(list($key, $value) = each($output))
{
echo "$key:$value"."
";
}
//方法二

function uniquearray($array)

reset($u_array, 1); for ($i=0,$n=count($u_array, 1);$i<$n;$i ) {$unduplicated_array[] = key($u_array, 1); next($u_array, 1); } return $unduplicated_array; } http://www.bkjia.com/PHPjc/631495.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/631495.htmlTechArticle在php中删除数组重复元素的函数有几个，一个是array_unique()另外就是array_flip()与array_uniqure()函数，但后者比前者性能要高几倍了，所以我只介...