Inheritance in PHP : inherit or use all properties Zand methods of one class(Parent or Base Class) to another class(child class).
Inheritance is the process of driving a new class from existing class,inherit the all features(Methods and Properties) of base class(Parent Class) in child class with extra features
class PHP
{
//PHP is parent class
}
class Mysql extends PHP
{
//Mysql is child class
}
		
class A
{
//code
}
class B extends A
{
//code
}
class C extends B
{
//code
} 
		
		In above example of multilevel inheritance class(B) is inherit class(A) property and methods.child class(C) is inherit class(B) property and method.
	
	In child class(C) have class(B) and class(C) features.
class php
{
//code
}
class mysql
{
//code
}
class html extends php mysql
{
//code
} 
//It does not support multiple inheritance.