Question

I read on php docs that isset() is faster than property_exists() and we should use a combination of both like

if (isset($this->fld) || property_exists($this, 'fld')) { 

But why can’t I just use isset then?

if (isset($this->fld)) {

Answer 1

Because property_exists will tell you if its even a defined property of the class/object where as isset doesnt make that distinction. for example:

class A {
  protected $hello;
}

class B {

}

using property_exists($this, 'hello') in class A will return true, while using it in class B will return false. isset will return false in both instances.