PHP - How to solve error "using $this when not in object context"?

Question

I've this trait class:

trait Example
{
    protected $var;

    private static function printSomething()
    {
        print $var;
    }

    private static function doSomething()
    {
        // do something with $var
    }
}

And this class:

class NormalClass
{
    use Example;

    public function otherFunction()
    {
        $this->setVar($string);
    }

    public function setVar($string)
    {
        $this->var = $string;
    }
}

But i'm getting this error: Fatal error: Using $this when not in object context.

How can i solve this issue? I can't use properties on a trait class? Or this isn't really a good practice?

where/how are you calling setvar()? to get that error you'd have to be doing something like $foo = NormalClass::setVar() or whatever. and for your printSomething, $var would be an undefined local variable. — Marc B
– Marc B, Commented Aug 17, 2015 at 15:03
that doesn't help, now it becomes "how/where are you calling otherFunction()"? You need to show the ENTIRE call chain. — Marc B
– Marc B, Commented Aug 17, 2015 at 15:05
You probably mean print static::$var;, since that method is static. Instance variables aren't going to help you there. — bishop
– bishop, Commented Aug 17, 2015 at 15:06
you are mixing instance-variables (which are part of the instance of a class) with class-variables (static, which are part of the class itself), $this->var VS. self::$var — birdspider
– birdspider, Commented Aug 17, 2015 at 15:06

Your Common Sense · Accepted Answer · 2023-09-02 20:41:48Z

20

Your problem is connected with differences between class's methods/properties and object's.

If you define a property as static - you should access it through your class like classname/self/parent ::$property.
If not static - then inside static property like $this->property.

For example:

trait Example   
{
    protected static $var;
    protected $var2;
    private static function printSomething()
    {
        print self::$var;
    }
    private function doSomething()
    {
        print $this->var2;
    }
}
class NormalClass
{
    use Example;
    public function otherFunction()
    {
        self::printSomething();
        $this->doSomething();
    }
    public function setVar($string, $string2)
    {
        self::$var = $string;
        $this->var2 = $string2;
    }
}
$obj = new NormalClass();
$obj -> setVar('first', 'second');
$obj -> otherFunction();

Static function printSomething can't access not static propertie $var! You should define them both not static, or both static.

edited Sep 2, 2023 at 20:41

Your Common Sense

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answered Aug 24, 2015 at 16:13

Dmitrii Cheremisin

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1 Comment

Your Common Sense Over a year ago

@JoSSte please don't add meaningless edits

Abdulla Nilam · Accepted Answer · 2022-09-20 12:48:58Z

0

Using $this when not in object context because of this code

$this->form_validation->set_rules('username','Username','required');

edited Sep 20, 2022 at 12:48

Abdulla Nilam

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answered Sep 15, 2022 at 17:20

Hannah

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