在usort函数中访问父类范围

Question

Is it possible to access the parent class's methods in this scenario, using usort()?

class MyClass {    
    public function isGreater($old,$new){
        return ($new - old > 0) ? true : false;
    }

    public function load($data){
        usort($data,function($a,$b){
            return $this->isGreater($a,$b) ? 1 : -1; // THIS IS THE PROBLEM LINE
        }
    }
}

I'm assuming since usort is using its own function scope, i can't access the public method isGreater(). Is there any way to do this? I can turn that method into a static function if it helps...

Answer 1

To access variables in an outer scope in an anonymous function, you need to use the use declaration:

public function load($data){
    $self = $this;
    usort($data,function($a,$b) use ($self){
        return $self->isGreater($a,$b) ? 1 : -1; // THIS IS THE PROBLEM LINE
    }
}

I've created a local variable $self because older versions of PHP don't allow accessing $this in a closure.