concatenated strings in class vars

causes parse errors

[ergophobe]

Another thing that's been bugging me for a while....

In classes in php 4.3.4

var $x = "string"; // no problem

$y = "string" . " that is a bit longer";
var $x = $y; // no problem

var $y = "string" . " that is a bit longer"; // parse error (unexpected ".")

Have they fixed that in more recent versions?

Tom

[Zipper]

In PHP 4, only constant initializers for var variables are allowed. To initialize variables with non-constant values, you need an initialization function which is called automatically when an object is being constructed from the class. Such a function is called a constructor.

I guess they have changed this in 5. Haven't seen it yet though.

[ergophobe]

Whoops, when I said

$y = "string" . " that is a bit longer";
var $x = $y; // no problem

I was hurrying. What I was actually doing was

define('MYSTRING', "string" . " that is a bit longer");
var $x = MYSTRING; // no problem

What is actually giving me problems is, in fact, a constant expression. In the following code:

define('TWO_PART_STRING', "This is a" . " two-part string.");

class myClass
{
var $x = "This is a string";
var $y = TWO_PART_STRING;
var $z = "This is a" . " two-part string.";
}

I get a parse error on the var $z line:

parse error: parse error, unexpected '.', expecting ',' or ';'

In other words, it appears that it is forbidden to concatenate strings, even when the resulting expression *is* a constant.

Tom

[coopster]

Yet the assignment itself is an expression, not a constant.

var $z = "This is still an" . " expression.";

[ergophobe]

Check! (and read the manual, which makes this clear).

I was thinking that if the values were available at parse time, it would replace the strings with tokens as efficiently as possible and make a constant.

I understand that it's not allowed, but it seems sort of crazy that

define("MY_EXP", "this is" . " an expression");
...
var $x = MY_EXP;

is allowed but

var $x = "this is" . " an expression";

is not.

From a parser/compiler point of view, I would think that all expressions that evaluate to constants would be tokenized upon parsing rather than at run time, but obviously not. I suppose the problem is that in PHP quoted strings often do no evaluate to constants because of variable substitutions ("in $strings like this") so you would end up doing too many passes.

I still find this annoying. It would make more sense to me if you could only assign default values of any sort in a constructor (like in C++).