Driver code
$ h = 0 ; $ k = 0 ; $ x = 2 ; $ y = 1 ; $ a = 4 ; if ( checkpoint ( $ h , $ k , $ x , $ y , $ a ) > 0 ) echo " Outside " ; else if ( checkpoint ( $ h , $ k , $ x , $ y , $ a ) == 0 ) echo " On ▁ the ▁ parabola " ; else echo " Inside " ; ? >