for the reference, I made a similar report a couple of years back:
http://bugs.php.net/52428

closing at as duplicate

This is not an exact duplicate.

That report was in fact about that '$GLOBALS["this"]' can be assigned using '$GLOBALS["this"] = ...', but cannot be assigned using 'global $this' or '$this = ...'.

This report is in fact about that if you set parameter name to 'this', you somewhy cannot read its members (although it is not forbidden to set parameter name per se, and to read or copy parameter value itself).

the root cause is the same/similar, we have basic checks in place which tries to catch any variable reference to $this when not in object context or when it would overwrite $this, but these checks are not perfect (as otherwise it would cause a more noticable performance loss on every variable read/write) which causes symptoms like this.
let's see if somebody has some idea about this exact situation, but I'm afraid that this won't be fixed for the same reasons as the other report.

IMO, just allow function parameter to be called '$this' (not in method, of course). It is useful for writing systems, which allow dynamic method addition. Like this:

class User extends \MyLib\Core\DynamicallyExtendableObject {
    function getSurname() {...}
    function getName() {...}
}

...

User::RegisterMethod('getFullname', function($this) {return $this->getName() . ' ' . $this->getSurname();});

Hmmm, I've realized that this now can be implemented even without creating explicit '$this' parameter (since PHP 5.4 supports bind/bindTo).


Never-the-less, per my opinion:

- Either this code should run fine:
    function f($this) {return $this->m;}
    f($someObject);

- Either this code should fail:
    function f($this) {}
    //I.e. just declaring function with '$this' parameter should cause error.

... but currently "function f($this) {}" (and even "function f($this) {print_r($this);} f($someObject);") runs fine, but "function f($this) {print_r($this->m);} f($someObject);" fails.

I.e. that checking for "PHP Fatal error: Using $this when not in object context" should happen not on using "->" operator, but on function declaration.

Fixed in PHP-7.1.
See https://wiki.php.net/rfc/this_var for more details.