define ('D',    '\d+(?:\.\d+)?');
 define ('G_MDB','/(\('.D.'[-+*\/]'.D.'\)|'.D. '[*\/]'.D.')/');
 define ('G_AS', '/'.D.'[-+]'.D.'/');
 define ('G_D',  '/('.D.')([-+*\/])('.D.')/');
//
 function  opers($matches) {
	 preg_match (G_D, $matches[ 0 ], $m);
	 if  ($m[ 2 ] == '*')  return  $m[ 1 ] * $m[ 3 ];
	 if  ($m[ 2 ] == '/')  return  $m[ 1 ] / $m[ 3 ];
	 if  ($m[ 2 ] == '+')  return  $m[ 1 ] + $m[ 3 ];
	 if  ($m[ 2 ] == '-')  return  $m[ 1 ] - $m[ 3 ];
}
//
$s = '(((8/2)/(2))*((2.7+1.3)+(6/3)-(16/8)+((9/3)+(2*3*(5-4)))))+6+(((16/8)/2)*(10+(3/1)-(4/2)+((8/2)+(7*8*(3-2)))))-3';
 while  ( preg_match ('/[-+*\/]/', $s)) {
	$s =  preg_replace ('/\(('.D.')\)/', '\1', $s);
	$s =  preg_replace_callback (G_MDB,'opers', $s);
	$s =  preg_replace_callback (G_AS, 'opers', $s);
}
 echo  $s;

 function  convertToPolishNotation($s) {
	$stack = $out = $items =  array ();
	 preg_match_all ('/(\d+(\.\d+)?|[-+*\/()])/', $s, $items);
	 foreach  ($items[ 0 ]  as  $c) {
		 if  ( is_numeric ($c)) $out[] = $c;
		 else  _addPnItem($stack, $out, $c);
	}
	 if  ( sizeof ($stack))
		$out =  array_merge ($out,  array_reverse ($stack));
	 return  $out;
}
//
 function  _addPnItem(&$stack, &$out, $c) {
	static $prior =  array ('*' =>  3 , '/' =>  3 , '+' =>  2 , '-' =>  2 , '(' =>  1 );
	 if  ( sizeof ($stack) ==  0  || $c == '(') {
		$stack[] = $c;
	}  elseif  ($c == ')') {
		 for  ($i =  sizeof ($stack) -  1 ; $i >=  0 ; --$i) {
			 if  ($stack[$i] == '(') {
				 array_pop ($stack);
				 break ;
			}
			 else  $out[] =  array_pop ($stack);
		}
	}  else  { // + - * /
		 for  ($i =  sizeof ($stack) -  1 ; $i >=  0 ; --$i) {
			$oper = $stack[$i];
			 if  ($prior[$oper] >= $prior[$c]) {
				$out[] = $oper;
				 unset ($stack[$i]);
			}
			 else   break ;
		}
		$stack[] = $c;
		$stack =  array_values ($stack);
	}
}
//
 function  calculatePolishNotation( Array  $s) {
	$pair =  array ();
	 foreach  ($s  as  $v) {
		 if  ( is_numeric ($v))
			$pair[] = $v;
		 else  {
			$size =  sizeof ($pair) -  2 ;
			 if  ($v == '*') $pair[$size] *=  array_pop ($pair);
			 if  ($v == '/') $pair[$size] /=  array_pop ($pair);
			 if  ($v == '+') $pair[$size] +=  array_pop ($pair);
			 if  ($v == '-') $pair[$size] -=  array_pop ($pair);
		}
	}
	 return  $pair[ 0 ];
}

//
$str = '(((8/2)/(2))*((2.7+1.3)+(6/3)-(16/8)+((9/3)+(2*3*(5-4)))))+6+(((16/8)/2)*(10+(3/1)-(4/2)+((8/2)+(7*8*(3-2)))))-3';
$str_pn = convertToPolishNotation($str);
$res = calculatePolishNotation($str_pn);
 echo  $res;

 function  convertToPolishNotation($s) {
	static $prior =  array ('*' =>  3 , '/' =>  3 , '+' =>  2 , '-' =>  2 , '(' =>  1 );
	$stack = $out = $items =  array ();
	// get operators & operands
	$d= null ;
	 for ($i= 0 ,$l= strlen ($s); $i<$l; ++$i) {
		 if  ( is_numeric ($s{$i}) || $s{$i}=='.') $d.=$s{$i};
		 else  {
			 if  ($d!= null ) {
				$items[]=$d;
				$d= null ;
			}
			$items[]=$s{$i};
		}
	}
	 if  ($d!= null )
		$items[]=$d;
	//
	 for ($i= 0 ,$m= sizeof ($items); $i<$m; ++$i) {
		 if  ( is_numeric ($items[$i]))
			$out[] = $items[$i];
		 else  { // addPn
			 if  ( sizeof ($stack) ==  0  || $items[$i] == '(') {
				$stack[] = $items[$i];
			}  elseif  ($items[$i] == ')') {
				 for  ($ii =  sizeof ($stack) -  1 ; $ii >=  0 ; --$ii) {
					 if  ($stack[$ii] == '(') {
						 array_pop ($stack);
						 break ;
					}
					 else  $out[] =  array_pop ($stack);
				}
			}  else  { // + - * /
				 for  ($ii =  sizeof ($stack)- 1 ; $ii>= 0 ; --$ii) {
					$oper = $stack[$ii];
					 if  ($prior[$oper] >= $prior[$items[$i]]) {
						$out[] = $oper;
						 unset ($stack[$ii]);
					}
					 else   break ;
				}
				$stack[] = $items[$i];
				$stack =  array_values ($stack);
			}
		}
	}
	 if  ( sizeof ($stack))
		$out =  array_merge ($out,  array_reverse ($stack));
	 return  $out;
}

class Obj {
	private $name = 'private var';
	public function getPrivate() {
		var_dump($this->name);
	}
}
class Obj2 extends Obj {
	protected $name = 'public var';
	public function getPublic() {
		var_dump($this->name);
	}
}
echo '<pre>';
$o = new Obj2();
$o->getPrivate();
$o->getPublic();