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Re: error message I don understand [message #174926 is a reply to message #174903] Mon, 18 July 2011 15:19 Go to previous messageGo to previous message
Thomas 'PointedEars'  is currently offline  Thomas 'PointedEars'
Messages: 701
Registered: October 2010
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Denis McMahon wrote:

> Thomas 'PointedEars' Lahn wrote:
>> In the end an oversimplified, wrong explanation. It is a syntactical
>> requirement, not a functional one:
>>
>> $a = x();
>
> Here you're assigning the return value of the function x() to the
> variable $a.
>
>> $a[0] = 42;
>
> Here you're writing to the variable $a (or rather, in this case, to an
> element of the array that is variable $a).
>
> Neither of these is trying to assign (write) a value to the return value
> of the function call.

Yes, it is. The return value of the function is a one-element array, and
with that assignment I am writing to the same memory area (or another memory
area that holds a copy of the former's content) by changing the first
element of the array. IOW, the return value is _not_ read-only.

> Whether you call the issue syntactical or not is just irrelevant and
> messing about with semantics.

You are mistaken. The issue is a syntactical one, not a functional one,
because a function call (currently) cannot occur on the left-hand side of an
assignment expression in PHP, *regardless* of the return value of function
to be called.

IOW, it does not make sense to say that "the return value is read-only" as
the function is *never* *called* and *no* return value is obtained in the
first place then. This is a rather important difference because syntax
errors are detected by the parser upon (JIT-)compilation already.


PointedEars
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