4. Given $A(0,0), B(1,0), C(0,2), D(3,3)$, point $P$ is any point in the plane, then the minimum value of $|P A|+|P B|+|P C|+|P D|$ is $\qquad$.
4. $2 \sqrt{3}+\sqrt{5}$ Hint: Point $P$ should be the intersection of the two diagonals of quadrilateral $A B C D$.

 untranslated part: 
$2 \sqrt{3}+\sqrt{5}$

Note: The mathematical expression is kept as is, since it is universally understood and does not require translation.