How to solve: Fatal error: Using $this when not in object context

$this is a special variable in PHP which can not be assigned. If it is accessed in a context where it does not exist, this fatal error is given.

This error can occur:

1. If a non-static method is called statically. Example:

   class Foo {
      protected $var;
      public function __construct($var) {
          $this->var = $var;
      }
   
      public static function bar () {
          // ^^^^^^
          echo $this->var;
          //   ^^^^^
      }
   }
   
   Foo::bar();

   How to fix: review your code again, $this could only used in object context, and should never in a static method. And also, static method should not access the non-static property. Use self::$static_property to access the static property.
2. If code from a class method has been copied over into a normal function or just the global scopeand keeping the $this special variable.
   How to fix: Review the code and replace $this with a different substitution variable.