【译】更快的模式实现PHP数组去重
【译】更快的方式实现PHP数组去重
原文:Faster Alternative to PHP’s Array Unique Function
概述
使用PHP的array_unique()函数允许你传递一个数组，然后移除重复的值，返回一个拥有唯一值的数组。这个函数大多数情况下都能工作得很好。但是，如果你尝试在一个大的数组里使用array_unique（）函数，它会运行地慢一些。
有一个比较好而且更快的函数array_flip()来替代使用array_unique()函数来创建唯一的数组。这个魔法般的函数会交换数组里面每一个元素的键和值，因为键值必须唯一，因此，你会得到跟array_unique()函数一样的结果。
更快的方式实现PHP数组去重
/* 创建一个包含重复值的，一共四个元素的数组 */$array = array('green','blue','orange','blue');/* 翻转数组，你将会得到唯一键值的数组 array('green'=>0,'blue'=>1,'orange'=>2); */$array = array_flip($array);/* 然后再翻转一次，将键和值重新放置，然后得到数组：array(0=>'green',1=>'blue',2=>'orange'); */$array = array_flip($array);
因为我们已经移除了一些元素，因此数组看起来不是正常的序列。比如我们可能会得到：array(0=>’A’,2=>’B’,5=>’C’);。在某些情况下，这不是一个问题，但是如果你需要数组的键值保持数字的序列，你可以使用一到两种方法解决键值乱序的问题。
使用array_merge修复数组的keys
添加array_flip之后的函数，将会对数组的键值排序并且让它们恢复到正常的序列，如：0,1,2,3…
$array = array('green','blue','orange','blue');$array = array_flip($array);$array = array_flip($array);/* 使用array_merge()函数修复键值*/$array = array_merge($array);
第二种方式，使用array_keys
注意，这种修复数组键值的方法比使用array_merge()函数稍微快了一点。你也可以在最后一步结合使用array_keys()函数(此函数返回翻转后的值)。然后当你翻转数组的值，键值就会根据顺序创建。
$array = array('green','blue','orange','blue');$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);
结论
非常简单，比起在大数组使用array_unique函数，有了一个有效的性能提升。
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