PHP Cannot access empty property error

Question

I am getting the following error and I can't seem to figure out why or how it's getting triggered.

Fatal error: Cannot access empty property in /home/content/p/l/a/plai1870/html/com/php/Bone/Compiler.php on line 18

Line 18 is

throw new LogicException($this->$compilers[$language]." is not a supported compiler.");

Here is Compiler.php

<?php
namespace Bone;
use LogicException;

class Compiler implements \Bone\Interfaces\Compiler {

    protected $compiler;

    protected $compilers = array(
        "php"           => "PHP",
        "as3"           => "ActionScript3",
        "javascript"    => "Javascript"
    );

    public function __construct($language) {
        $language = strtolower($language);
        if (!isset($this->$compilers[$language])) {
            throw new LogicException($this->$compilers[$language]." is not a supported compiler.");
        }
        $compiler = "\Bone\Compilers\\".$this->$compilers[$language]."\Compiler";
        $this->compiler = new $compiler();
    }

    public function buildDefinition($object, $path = null) {
        return $this->compiler()->buildInterface($object, $path);
    }

    public function buildObject($object, $path = null) {
        return $this->compiler->buildObject($object, $path);
    }   

    public function parameters($method) {
        return;
    }

    public function save($data, $path) {
        return;
    }
}
?>

EDIT And I'm calling it with:

$compiler = new \Bone\Compiler("php");

$this->$compilers ---> $this->compilers - remove the $ after ->. — hakre
– hakre, Commented Nov 7, 2012 at 16:31

hakre · Accepted Answer · 2012-11-07 16:33:02Z

7

Sorry if this is the most obvious, but:

throw new LogicException($this->$compilers[$language]." is not a supported compiler.");

As it has been checked that the property does not exists, shouldn't it be:

throw new LogicException("$language is not a supported compiler.");

?

Edit:

$this->$compilers[$language]
       ^- variable property

Remove the $ there:

$this->compilers[$language]

Then you can check if the entry in the array is set, not if a propery with the name of the value inside the (unset) array $compilers (local variable) is set.

When developing, always switch on warnings and notices (highest error level you can imagine) to not run into these problems without having PHP warn you first.

edited Nov 7, 2012 at 16:33

answered Nov 7, 2012 at 16:27

hakre

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5 Comments

Nathan L. Over a year ago

Sorry, if you see my edit, you will see that it does exist. Compiler::compilers has a key 'php' so it should not be throwing the error. $this->compilers does exist if you look at the source!

Nathan L. Over a year ago

But I do see the error there. But I also get it on the next line when it sets $compiler = "\Bone\Compilers\\".$this->$compilers[$language]."\Compiler"; after checking if the key exists.

hakre Over a year ago

What you do not understand is the one $ too much. the local variable $compilers is not defined. The property is defined (it has the same name), however you are not accessing it there. Try with $this->compilers[$language] instead.

Nathan L. Over a year ago

Wow, now I feel like an idiot. I think it's about time for some sleep!

hakre Over a year ago

I can not judge about your sleep, but this is some error everybody does at some time ;)

gen_Eric · Accepted Answer · 2012-11-07 16:31:20Z

3

Your array is $this->compilers, not $this->$compilers.

$compilers doesn't exist in your function, so $this->$compilers was looking for a blank property.

answered Nov 7, 2012 at 16:31

gen_Eric

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