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How to achieve quick deduplication effect of php array elements
How to achieve quick deduplication effect of php array elements
1. Use the array_unique method to deduplicate
To deduplicate array elements, we generally use the array_unique method. This method can deduplicate the elements in the array.
<?php$arr = array(1,1,2,3,3,3,4,4,5,6,6,7,8,8,9,9,9);$arr = array_unique($arr);$arr = array_values($arr); print_r($arr);?>
Output:
Array(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9)After deduplication, the key values will be out of order. You can use array_values to reorder the key values.
2. Use array_unique method to remove duplicates for efficiency
<?php$arr = array();// 创建100000个随机元素的数组for($i=0; $i<100000; $i++){ $arr[] = mt_rand(1,99);
}// 记录开始时间$starttime = getMicrotime();// 去重$arr = array_unique($arr);// 记录结束时间$endtime = getMicrotime();$arr = array_values($arr);echo 'unique count:'.count($arr).'<br>';echo 'run time:'.(float)(($endtime-$starttime)*1000).'ms<br>';echo 'use memory:'.getUseMemory();/**
* 获取使用内存
* @return float
*/function getUseMemory(){
$use_memory = round(memory_get_usage(true)/1024,2).'kb'; return $use_memory;
}/**
* 获取microtime
* @return float
*/function getMicrotime(){
list($usec, $sec) = explode(' ', microtime()); return (float)$usec + (float)$sec;
}?>unique count:99
run time:653.39303016663ms
use memory:5120kb
Use the array_unique method to remove duplicates. The running time takes about 650ms and the memory usage is about 5m
3. Faster Array deduplication method
php has a key-value exchange method array_flip. We can use this method to deduplicate. Because of key-value exchange, the original duplicate values will become the same key.
Then perform a key-value exchange and exchange the keys and values back to complete deduplication.
<?php$arr = array();// 创建100000个随机元素的数组for($i=0; $i<100000; $i++){ $arr[] = mt_rand(1,99);
}// 记录开始时间$starttime = getMicrotime();// 使用键值互换去重$arr = array_flip($arr);$arr = array_flip($arr);// 记录结束时间$endtime = getMicrotime();$arr = array_values($arr);echo 'unique count:'.count($arr).'<br>';echo 'run time:'.(float)(($endtime-$starttime)*1000).'ms<br>';echo 'use memory:'.getUseMemory();/**
* 获取使用内存
* @return float
*/function getUseMemory(){
$use_memory = round(memory_get_usage(true)/1024,2).'kb'; return $use_memory;
}/**
* 获取microtime
* @return float
*/function getMicrotime(){
list($usec, $sec) = explode(' ', microtime()); return (float)$usec + (float)$sec;
}?>unique count:99
run time:12.840032577515ms
use memory:768kb
Use array_flip method to remove duplicates, the running time takes about 18ms, the memory usage is about 2m
. Therefore, using the array_flip method to remove duplicates takes longer than using the array_unique method. The running time is 98%, memory usage reduced4/5;
This article explains how to achieve the rapid deduplication effect of PHP array elements. For more related content, please pay attention to the PHP Chinese website.
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