PHP：带有可能为空变量的条件语句
我正在创建一个自定义搜索表单，当我尝试对结果进行排序时，我会显示所有对象而不是匹配的条件。我发现的原因是表单中的某些输入没有默认值，并且当稍后在条件语句中未声明默认值（用于排序）时，它只会显示所有对象，无论是否满足其他要求或不是。我尝试应用 OR 语句，其中特定变量可以为空，但它给出了相同的结果。就像这样 -
<?php if ($bedrooms >= $min_rooms
&& $bedrooms <= $max_rooms
&& $space >= $min_space
&& $space <= $max_space
&& $price >= $min_price
&& $price <= $max_price
&& $sel_type == $type
|| $sel_type == ''
&& $country == $sel_country
|| $sel_country == '' ) { ?>
（参见最后两个陈述） 我正在考虑在包含条件语句之前检查条件语句中的每个变量，但感觉像是不必要的代码。你会怎么做？
I'm creating a custom search form and when I try and sort the results I get all the objects displayed instead of the matched criteria. The reason I discovered was that some of the inputs from the form don't have a default value and when this is not declared in the conditional statement later on (for sorting) it just shows all the objects, whether the other requirements are met or not. I tried applying an OR statement with the specific variables able to be empty, but it gave the same result. Like so -
<?php if ($bedrooms >= $min_rooms
&& $bedrooms <= $max_rooms
&& $space >= $min_space
&& $space <= $max_space
&& $price >= $min_price
&& $price <= $max_price
&& $sel_type == $type
|| $sel_type == ''
&& $country == $sel_country
|| $sel_country == '' ) { ?>
(See the last two statements)
I was thinking of checking each variable in the conditional statement before including it but it feels like unnecessary code. How would you do it?
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&&运算符的优先级高于||运算符，因此您的表达式当前按如下方式分组，可能不是您想要的：尝试添加这样的括号实现正确分组：
The
&&operator has a higher precedence than the||operator, so your expression is currently grouped like this, probably not what you want:Try adding parentheses like this to achieve correct grouping:
您的表达式可能会失败，因为
&&运算符具有更高的优先级 比||操作。这意味着像这样的表达式：等价于此（通过使用括号突出显示运算符优先级）：
要解决此问题，请将
||表达式放在括号中：此外，您的表达式可能更易于阅读和维护如果您使用一些辅助函数，例如
Between 函数：那么您的表达式将显示为：
Your expression may fail as the
&&operator has a higher precedence than the||operation. That means an expression like this:is equivalent to this (operator precedence highlighted by using parentheses):
To fix that put the
||expressions in parentheses:Additionally, your expression is probably easier to read and to maintain if you use some helper functions like a
betweenfunction:Then your expression reads: