CODEWITHSUNDEEP
phpoopvariables
Kalreg
Kalreg

Reputation: 941

PHP Declaring variable in class that is made from another variable

I yesterday discovered strange issue in my class - hope you know some answers. Consider such a class:

class Person {

public $height = 90;
public $weight = $this->height * 0.8;

}

This class returns an error "Parse error: syntax error, unexpected T_VARIABLE" and it seems i can not declare variable in class that is variable itself. Can I only set "static" values to variables in class (i mean static like directly declared like string or int no static like "static $var = 'xyz'";Why is that happening?

Thanks, Kalreg.

Upvotes: 1

Views: 39

Answers (2)

Asenar
Asenar

Reputation: 7010

properties cannot have dynamic values in the class definition, but you can define the weight in the __construct method if you want: 

class Person {

  public $height = 90;
  public $weight;

  public function __construct()
  {
    $this->weight = $this->height * 0.8;
  }

}

Upvotes: 0

Alma Do
Alma Do

Reputation: 37365

Currently, you can use only constant expressions when defining default properties values in PHP. That means you can not use anything that will be evaluated at run-time. Since $this refers to dynamic instance value, it is run-time, obviously, and cannot be used in such definitions.

Upvotes: 5

Related Questions