帮助理解括号的使用方式......菜鸟问题

Question

I understand what the following line does but i don't understand how the brackets are used? I have always used brackets in an if, while and other statements but i have never used them in this fashion.

Are there rules to using them this way, should i not use them in this way? Any help would be appreciated... Thanks

${$key} = $temp;

Answer 1

In that specific case, there is effectively no difference between using brackets and not.

So your code is equivalent to the following:

$$key = $temp;

The brackets are typically used to force PHP to interpolate variables in strings, which isn't necessary in this case.

Using the brackets is very helpful for reducing ambiguity in a statement using array indices:

${$array[0]} = $temp;

As opposed to

$$array[0] = $temp;

The parser will think that you meant ($$array)[0], not $($array[0])