Getting a value of a dynamic class and dynamic property

Question

Is it possible to get the value of a instance variable that is a class and the value needed to get is just a string? I'm getting strings that are "$user->Prop" lets say, and I want to eval() this string to get the value, but it seems the eval function doesn't know about $user even though it is an instance variable.

$user->Prop = 3;
$a = "user->Prop";
$val = eval($$a); //how to get 3 with this string?

I know I can do

$prop = "prop";
$user->$prop;

and get 3, but in this case I'm trying to only pass in the variable I want to test and get the value in short.

what does your class look like ? I think what you are trying to do should be simpler than this. — Maximus2012, Jul 17 '13 at 20:19
it would be far too much code to show, I did summarize what is happening in the code snip above. — Justin T. Watts, Jul 17 '13 at 20:20
so I am assuming $user is an object of the user class. Something like $user = new User(). if Prop is declared as public in the user class then you should be able to get the value by doing something like: var_dump($user->Prop) — Maximus2012, Jul 17 '13 at 20:22
yes, but I only have a value of string(11)"$user->Prop" and want to eval to 3 in this case. — Justin T. Watts, Jul 17 '13 at 20:25
ah, it turns out the eval function will return a value, but I must use return so in this case if I'm receiving "$user->Prop" I have to do $a = "/$user->Prop"; $val = eval("return $a;"); — Justin T. Watts, Jul 17 '13 at 20:33

score 3 · Accepted Answer · answered Jul 17 '13 at 20:26

3

eval does not return result of evaluated, if you want to store property value in $val, you have to include it in evaluated string:

$a = 'user->prop';
$eval = '$val = $'.$a.';';

eval($eval);
var_dump($val);

answered Jul 17 '13 at 20:26

dev-null-dweller

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best solution, I've put a method to eval the value by putting return in the string, this got me on the right track, thanks! – Justin T. Watts Jul 17 '13 at 20:37

Rooster · Answer 2 · 2013-07-17T20:37:23.873

2

This won't work because you can't represent the -> dynamically.

$user->Prop = 3;
$a = "user->Prop";
$val = ${$a};

But you can do this:

$user->Prop = 3;
$a = "user";
$b = "Prop";
$val = ${$a}->$b;

edited Jul 17 '13 at 20:37

answered Jul 17 '13 at 20:26

Rooster

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@tlenss ahhh. nice catch. Started up my Wamp and double checked. Edited my answer to correct your find. – Rooster Jul 17 '13 at 20:39

score 0 · Answer 3 · answered Jul 17 '13 at 20:34

0

Turns out if I have a string(11)"$user->Prop" and it is stored in $a what I need to do is:

$val = eval("return $a;");

need to read the docs more closely...good to write about it I guess though.

answered Jul 17 '13 at 20:34

Justin T. Watts

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Getting a value of a dynamic class and dynamic property

3 Answers3