问题描述
说例如我有...
$ var1 =ABC
$ var2 = 123
在特定条件下,我想交换两个像这样...
$ var1 = 123
$ var2 =ABC
是否有PHP函数用于执行此操作,而不必创建第三个变量保留其中一个值然后重新定义每个值,就像这样......
$ b
$ var3 = $ var1
$ var1 = $ var2
$ var2 = $ var3
简单的任务它可能更快地使用第三个变量,我总是可以创建自己的功能,如果我真的想。只是想知道是否存在类似的东西?
更新:使用第三个变量或将其封装在函数中是最佳解决方案。它干净简单。我更多地出于好奇而问了这个问题,并且选择的答案是下一个最佳选择。只需使用第三个变量。
没有内置函数。
正如很多人所说,有3种方法可以做到这一点:
函数swap1(& $ x,& $ y){
$ x ^ = $ y ^ = $ x ^ = $ y;
函数swap2(& $ x,& $ y){
list($ x,$ y)= array($ y,$ x);
}
函数swap3(& $ x,& $ y){
$ tmp = $ x;
$ x = $ y;
$ y = $ tmp;
}
我在1000次迭代的for循环下测试了3种方法,它们中速度最快:
- swap1 =得分的近似平均值 0.19 秒。
- swap2 =得分的近似平均值为0.42秒。
- swap3 = 0.16分钟的近似平均值。
为了可读性/可写性,IMO发现swap3比其他两个函数要好。
更新2017:
- swap2总是比其他类型的因为函数调用而慢。
- swap1和swap3的性能速度非常相似,但大多数情况下,swap3的速度稍快。
- 警告: swap1仅适用于数字!
Say for instance I have ...
$var1 = "ABC"
$var2 = 123
and under certain conditions I want to swap the two around like so...
$var1 = 123
$var2 = "ABC"
Is there a PHP function for doing this rather than having to create a 3rd variable to hold one of the values then redefining each, like so...
$var3 = $var1
$var1 = $var2
$var2 = $var3
For such a simple task its probably quicker using a 3rd variable anyway and I could always create my own function if I really wanted to. Just wondered if something like that exists?
Update: Using a 3rd variable or wrapping it in a function is the best solution. It's clean and simple. I asked the question more out of curiosity and the answer chosen was kind of 'the next best alternative'. Just use a 3rd variable.
There isn't a built-in function.
As many mentioned, there are 3 methods to do this:
function swap1(&$x,&$y) {
$x ^= $y ^= $x ^= $y;
}
function swap2(&$x,&$y) {
list($x,$y) = array($y,$x);
}
function swap3(&$x,&$y) {
$tmp=$x;
$x=$y;
$y=$tmp;
}
I tested the 3 methods under a for-loop of 1000 iterations, to find the fastest of them:
- swap1 = scored approximate average of 0.19 seconds.
- swap2 = scored approximate average of 0.42 seconds.
- swap3 = scored approximate average of 0.16 seconds.
And for readability/writability, IMO I find swap3 is better than the other 2 functions.
UPDATE 2017:
- swap2 is always slower than the other ones because of the function call.
- swap1 and swap3 both performance speed are very similar, but most of the time swap3 is slightly faster.
- Warning: swap1 works only with numbers!
这篇关于是否有一个用于交换两个变量值的PHP函数?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!