1.2.585. Interfaces Don’t Ensure Properties

When using an interface as a type, properties are not enforced. They might be not available, and lead to a Fatal Error.

An interface is a template for a class, which specify the minimum amount of methods and constants. Properties are never defined in an interface, and should not be relied upon.

Properties may be defined in an abstract class.

<?php

interface i {
    function m () ;
}

class x implements i {
    public $p = 1;

    function m() {
        return $this->p;
    }
}

function foo(i $i, x $x) {
    // this is invalid, as $p is not defined in i, so it may be not available
    echo $i->p;

    // this is valid, as $p is defined in $x
    echo $x->p;
}

?>

See also Interface And Abstract Class.

1.2.585.1. Suggestions

• Use classes for type when properties are accessed

• Only use methods and constants which are available in the interface

• Use an abstract class

1.2.585.2. Specs

Short name	Interfaces/NoGaranteeForPropertyConstant
Rulesets	All, Analyze, Changed Behavior, Class Review
Exakat since	1.9.5
PHP Version	All
Severity	Minor
Time To Fix	Quick (30 mins)
Precision	High
Features	interface
Available in	Entreprise Edition, Exakat Cloud