Static properties can be accessed directly without creating an instance of a class. Static properties can be declared by using the static keyword.

To access a static property we need to write the class name followed by a double colon (::), and the property name.

Example:

<?php
class pi {
  public static $value = 3.14;
}
// Getting static property
echo pi::$value;
?>

A static method can be accessed from a method in the same class using the self keyword followed by a double colon (::), and the method name.

Example

<?php
class pi {
  public static $value = 3.14159;
  public function staticValue() {
    return self::$value;
  }
}
 
$pi = new pi();
echo $pi->staticValue();
?>

If we need to call a static property from a child class, we can use the parent keyword inside the child class.

Example:

<?php
class pi {
  public static $value = 3.14;
}
class x extends pi {
  public function xStatic() {
    return parent::$value;
  }
}
// Get value of static property directly via child class
echo x::$value;
?>