What are the scope areas in PHP?

In PHP, the following scopes exist:

1. Local: Variables declared inside a function. Accessible only within that function. The variable's lifetime is until the function executes.

   // Local scope
   function myFunc() {
       $localVar = "Visible only here";
       echo $localVar;
   }
   myFunc();
   // echo $localVar; // Error! Variable does not exist in the global scope
   

2. Global: Variables declared outside functions. Accessible in the global namespace. Inside functions, to access them, use the global keyword or the $GLOBALS superglobal array.

   // Global scope
   $globalVar = "Visible everywhere";
   
   function anotherFunc() {
       global $globalVar; // Access to global variable
       echo $globalVar;
   }
   anotherFunc();
   echo $globalVar; // Access to global variable
   

3. Static: Variables declared inside a function with the static keyword. They retain their value between function calls but are only accessible within that function (similar to local, but with state preservation).

   // Static scope
   function countingFunc() {
       static $staticVar = 0; // Initialized only on the first call
       $staticVar++;
       echo $staticVar;
   }
   
   countingFunc(); // Outputs 1
   countingFunc(); // Outputs 2
   countingFunc(); // Outputs 3
   

4. Class/Object Scope: Variables (properties) and functions (methods) inside a class. Access depends on access modifiers (public, protected, private).

   • public: Accessible from everywhere (inside class, outside, from subclasses).
   • protected: Accessible inside the class and subclasses.
   • private: Accessible only within the class where declared.

   // Class/Object scope
   class MyClass {
       public $publicProperty = "Public";
       protected $protectedProperty = "Protected";
       private $privateProperty = "Private";
   
       public function showProperties() {
           echo $this->publicProperty;
           echo $this->protectedProperty;
           echo $this->privateProperty;
       }
   }
   
   $obj = new MyClass();
   echo $obj->publicProperty; // Accessible
   // echo $obj->protectedProperty; // Error - not accessible outside
   // echo $obj->privateProperty; // Error - not accessible outside
   $obj->showProperties(); // Methods inside the class have access to all properties
   

It is important to understand the difference between scope and namespace. Scope defines the accessibility of variables/functions/constants/classes in a certain execution context. Namespace prevents name conflicts.