when used with an object variable, it access the member functions or variables contained in the class.
class testing {
function example()
{
echo "Hello World";
}
}
$var = new testing(); //create object
$var->example(); //access our function - echo's hello world
when used with $this, inside a class, it references the local class variables.
class testing2 {
var $test = 5;
function showTest()
{
echo $this->test;
}
}
$var = new testing2();
$var->showTest(); //echo's 5
think of it as a way to point to and access class functions and variables from an object or inside the class.