Sincerely
Negin Nickparsa
On Mon, Aug 25, 2014 at 12:51 PM, Domain nikha.org <mail@xxxxxxxxx> wrote:
> > Christoph Becker am Montag, 25. August 2014 - 16:25:
> > 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 $zero instead, or maybe an array.
> >
> > > I am totally mixed up.
> >
> > [1]
> > <
> http://php.net/manual/en/language.types.string.php#language.types.string.parsing.simple
> >
> > [2]
> > <
> https://github.com/php/php-langspec/blob/master/spec/10-expressions.md#user-content-variable-name-creation-operator
> >
> >
> > --
> > Christoph M. Becker
> >
>
> The manual is not realy clear in this point. My practical expierence says
> this:
> an expression like "${....}" is always evaluated as string. ${0} creates a
> variable named "0", because "0" is not the integer, that would be illegal.
>
> And BTW: ${0000.578} gives you "0000_578", because dots in variable names
> are not allowed and automatically converted to underscores. And it is NOT
> evaluated to a float.
>
> Confusing, and indeed avoid it!
>
>
> The fabulous type juggling of PHP operates on the values, not the names of
> variables!
>
>
Why the hell you really need a variable named "0"?
:) Niklaus
Actually I guess nobody need that and you're absolutely right.
It was a practice question that I failed to answer correctly and I was
frustrated too.
Thank you so much for your guidance.
Since variables are denoted by the lead $ character I can't think of a good
reason why a variable can't start with a number after the $ since the
parser already knows it's working with a variable. I would imagine that
it's a convention carried forward from C or other languages.
Robert, Thank you so much for nice explanation and examples I really
appreciated.
--
> Niklaus
>
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