Extends a class within php, as described in more detail here. Basically is making a second class extended from the first class with either making amendments to some of the functions or adding some, this makes the second class the version 2 from the first class (version 1).
The extended class can still call the parent (version 1) class via the
parent::
syntax, which basically means, calling the parent class to do something, for example the parent class may setup the variables of a array whilst the extended version 2 class may sort them into alphabetical order.
Here some code that may make more sense.
HiFromMe();
$base->BaseFunction();
$extended = new ExtendedClass();
$extended->HiFromMe();
echo "\nYou can still call the base functions because you extended it";
$extended->BaseFunction();
echo "\nTo call from within a function";
$extended->CallBaseFunction();
?>
and the output would be...
Hi from the base class
Hi from base function
Hi from the extended class
You can still call the base functions because you extended it
Hi from base function
To call from within a function
Calling base (parent) class
Hi from base function