PHP object property from class variable? [duplicate]

Question

Why does this work

foreach ($items as $i) {
    $dataTitle = $this->dataTitle;
    $title = $i->$dataTitle;
}

when this doesn't?

foreach ($items as $i) {
    $title = $i->$this->dataTitle;
}

Is there a better way to do this?

I don't think its quite a duplicate. I'm not concatenating things for one. I was thinking $this->dataTitle was a variable in and of it self; a class variable. With that thinking I didn't understand why it didn't work. — Justin808
– Justin808, Commented May 16, 2013 at 6:24
Nonetheless, it covers the correct syntax you should use for this concept. — Ja͢ck
– Ja͢ck, Commented May 16, 2013 at 6:25
Possibly, but just because two questions have the same answer does not mean they are the same question. Feel free to mark it for close, your choice. I just commented as to why I thought it wasn't a duplicate. — Justin808
– Justin808, Commented May 16, 2013 at 6:27

Barmar · Accepted Answer · 2013-05-16 06:04:14Z

4

Try this:

$title = $i->{$this->dataTitle};

Your expression is being parsed as:

$title = ($i->$this)->dataTitle;

answered May 16, 2013 at 5:57

Barmar

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2 Comments

PHP Parse error: syntax error, unexpected '(', expecting identifier (T_STRING) or variable (T_VARIABLE) or '{' or '$' in SimpleList.php

Fixed it. An expression after -> has to be in {}.

BlitZ · Accepted Answer · 2013-05-16 06:09:30Z

3

$this referes to current object parsed in not obvious order. You need to use {expr} notation, to dynamicly evaluate property name.

Try to use {} around $this->dataTitle:

$title = $i->{$this->dataTitle};

Look at bottom part of last example in variable variables section of manual.

answered May 16, 2013 at 5:57

BlitZ

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Bingo. Though why {} and not ()? I thought () was used to group things for order of operations, and that seems to be what is going on here?

@Justin808 It is not group order operation. It is property evaluation operation.