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\n<\/p>\n
Basic OOP access restrictions are made for encapsulation.<\/p>\n
Public access – allows access from anywhere (outside\/inside).<\/p>\n
Protected access – allows access from inside class itself or the class that inherits(child class).<\/p>\n
Private access – allows access only WITHIN class, not child<\/p>\n
In additional, to deeply understand what is OOP and follow the GOOD HABBITS for OOP from the beginning – I suggest you to read SOLID<\/a>, the five first oop principles. They are the KEY to the OOP Approach. Read and understand these. Hope this helps.<\/p>\n Regards,<\/p>\n VR<\/p>\n<\/p><\/div>\n
\nYou may also want to read GRASP<\/a> OOD Principles.
\nThere is also a common accepted coding standards around – PEAR Coding Standard<\/a><\/p>\nPublic example<\/h1>\n
Class A {\n public $a = \"hello oop world\";\n public function getA()\n {\n return $this->a;\n }\n}\n# call successful in any case\n$a = new A;\n$a->getA(); \/\/ success\necho $a->a \/\/ success due to it's access public\n<\/code><\/pre>\nProtected Example<\/h1>\n
Class A {\n public $a = \"hello OOP world\";\n protected $_b = \"Here we test protected\";\n public function getA() {\n return $this->a;\n }\n}\n\nClass B extends A {\n public function getB() {\n return $this->_b;\n }\n}\n\n# test\n$a = new A; #init\n$b = new B; #init\necho $a->a; \/\/ success - prints \"hello oop world\"\necho $a->_b; \/\/ fails with access error.\necho $a->getA(); \/\/ success print hello oop world\necho $b->getA(); \/\/ also prints hello oop world (inherited all of the parent class!)\necho $b->getB(); \/\/ return the $_b ! why? it is inherited and we made public getter in child class!\n<\/code><\/pre>\nPrivate example<\/h1>\n
Class A {\n private $_sharedProperty = \"Sometimes Private is good!\"\n public function parentGetter() {\n return $this->_sharedProperty;\n }\n}\n\nClass B {\n public childGetter() {\n return $this->_sharedProperty;\n }\n}\n\n# Now we test, as we can see, both methods trying to access shared property.\n$parent = new A; #instantiate\n$child = new B; #instatiate\necho $parent->_sharedProperty; \/\/ Fails with access restricted.\necho $parent->parentGetter(); \/\/ print the shared property of instance.\necho $child->_sharedProperty \/\/ Fails also with access restricted.\necho $child->childGetter(); \/\/ FAILS ! Why? Private is not available to child!\n<\/code><\/pre>\n