PHP Elseif 三元运算符
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PHP Elseif Ternary Operators
提问by Jon
I am trying to convert the following code into a Ternary Operator, but it is not working and I am unsure why. I think my problem is that I do not know how to express the elseifoperation in ternary format. From my understanding and elseifis performed the same way as an ifoperation by using the format : (condition) ? 'result'.
我正在尝试将以下代码转换为三元运算符，但它不起作用，我不确定为什么。我想我的问题是我不知道如何elseif用三元格式来表达操作。根据我的理解，elseif它的执行方式与if使用 format的操作相同: (condition) ? 'result'。
if ($i == 0) {
$top = '<div class="active item">';
} elseif ($i % 5 == 0) {
$top = '<div class="item">';
} else {
$top = '';
}
$top = ($i == 0) ? '<div class="active item">' : ($i % 5 == 0) ? '<div class="item">' : '';
回答by Samuel Cook
$top = ($i == 0) ? '<div class="active item">' : (($i % 5 == 0) ? '<div class="item">' : '');
you need to add parenthesis' around the entire else block
您需要在整个 else 块周围添加括号
回答by losthorse
The Ternary Operator doesn't support a true if... else if... else...operation; however, you can simulate the behavior by using the following technique
三元运算符不支持真正的if... else if... else...操作；但是，您可以使用以下技术模拟行为
var name = (variable === 1) ? 'foo' : ((variable === 2) ? 'bar' : 'baz');
I personally don't care for this as I don't find it more readable or elegant. I typically prefer the switchstatement.
我个人并不关心这个，因为我不觉得它更具可读性或优雅性。我通常更喜欢这种switch说法。
switch (variable) {
case 1 : name = 'foo'; break;
case 2 : name = 'bar'; break;
default : name = 'bas'; break;
}
回答by Bhaskar Pramanik
Too late probably to share some views, but nevertheless :)
分享一些观点可能为时已晚，但仍然:)
- Use if - else if - else for a limited number of evaluations. Personally I prefer to use if - else if - else when number of comparisons are less than 5.
- Use switch-case where number of evaluations are more. Personally I prefer switch-case where cases are more than 5.
- Use ternary where a single comparison is under consideration (or a single comparison when looping), or when a if-else compare is needed inside the "case" clause of a switch structure.
- Using ternary is faster when comparing while looping over a very large data set.
- 使用 if - else if - else 进行有限数量的评估。我个人更喜欢在比较次数小于 5 时使用 if - else if - else。
- 在评估次数较多的情况下使用 switch-case。就个人而言，我更喜欢 case 超过 5 的 switch-case。
- 在考虑单个比较（或循环时的单个比较）时，或者在 switch 结构的“case”子句中需要 if-else 比较时，使用三元。
- 在循环非常大的数据集时进行比较时，使用三元会更快。
IMHO Its finally the developer who decides the trade off equation between code readability and performance and that in turn decides what out of, ternary vs. if else-if else vs. switch-case, can be used in any particular situation.
恕我直言，最终由开发人员决定代码可读性和性能之间的权衡等式，然后决定可以在任何特定情况下使用三元与 if else-if else 与 switch-case 中的什么。
