Overloading in oop is same as overloading in real word. In real word overloading means assigning extra work to same machine or person. In oop method overloading is same. By process of method overloading you are asking your method to some extra work. Or in some cases we can say some different work also.
Normally method overloading in oop is managed on the basis of the argument passed in function. We can achieve overloading in oop by providing different argument in same function.
Overriding in php is very easy. As we know that overriding is process of modifying the inherited method. So in case of inheritance you only need to create method with same name in your child class which you want to override.