Negin Nickparsa wrote:
> why ${0} is valid but ${0 is not valid?
> it means that curly braces evaluate what's inside them
No, at least not in the general case. This notation is called "simple
syntax" in the PHP manual[1] and "Variable-Name Creation
Operator/Expression" in the current draft of the PHP language
specification[2].
> and that's why we
> cannot have ${0?
>
> variables shouldn't start from 0 so it means that it started from braces?
> if yes why I cannot have ${0? and what is the variable here finally? $0 is
> what it interprets?
Yes, indeed. However, the notation $0 would be a syntax error.
> if yes so it is not a legal variable
Well, actually it is a legal variable, but it might better be avoided to
use such variables. They are confusing, and I can't think of any
advantage in using such variables. Use $zero instead, or maybe an array.
> I am totally mixed up.
[1]
<http://php.net/manual/en/language.types.string.php#language.types.string.parsing.simple>
[2]
<https://github.com/php/php-langspec/blob/master/spec/10-expressions.md#user-content-variable-name-creation-operator>
--
Christoph M. Becker
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