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A faster way to implement array deduplication in PHP

高洛峰

Jan 14, 2017 pm 03:03 PM

php array

Overview

Using PHP's array_unique() function allows you to pass an array and then remove duplicate values and return an array with unique values. This function works well most of the time. However, if you try to use the array_unique() function on a large array, it will run slower.

There is a better and faster function array_flip() instead of using the array_unique() function to create a unique array. This magical function will swap the key and value of each element in the array. Since the key value must be unique, you will get the same result as the array_unique() function.

A faster way to implement PHP array deduplication

/* 创建一个包含重复值的，一共四个元素的数组 */
$array = array(&#39;green&#39;,&#39;blue&#39;,&#39;orange&#39;,&#39;blue&#39;);
/* 翻转数组，你将会得到唯一键值的数组
array(&#39;green&#39;=>0,&#39;blue&#39;=>1,&#39;orange&#39;=>2); */
$array = array_flip($array);
/* 然后再翻转一次，将键和值重新放置，然后得到数组：array(0=>&#39;green&#39;,1=>&#39;blue&#39;,2=>&#39;orange&#39;); */
$array = array_flip($array);

Because we have removed some elements, the array does not look like a normal sequence. For example, we may get: array(0=>'A',2=>'B',5=>'C');. In some cases, this is not a problem, but if you need the array keys to remain in numerical order, you can use one or two methods to solve the problem of key values being out of order.

Use array_merge to repair the keys of the array

The function after adding array_flip will sort the key values of the array and restore them to the normal sequence, such as: 0 ,1,2,3…

$array = array(&#39;green&#39;,&#39;blue&#39;,&#39;orange&#39;,&#39;blue&#39;);
$array = array_flip($array);
$array = array_flip($array);
/* 使用array_merge()函数修复键值*/
$array = array_merge($array);

The second way is to use array_keys

Note that this method of repairing the array key value is slightly faster than using the array_merge() function . You can also use the array_keys() function in the last step (this function returns the flipped value). Then when you flip the values in the array, the keys are created in order.

$array = array(&#39;green&#39;,&#39;blue&#39;,&#39;orange&#39;,&#39;blue&#39;);
$array = array_flip($array);
/* 跟第一个例子一样，但是现在我们先提取数组的键值 */
$array = array_keys($array);

Conclusion

It is very simple. Compared with using the array_unique function in large arrays, there is an effective performance improvement.

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