Minimum revolutions to move center from ( x1 , y1 ) to ( x2 , y2 )
< ? php function minRevolutions ( $ r , $ x1 , $ y1 , $ x2 , $ y2 ) { $ d = sqrt ( ( $ x1 - $ x2 ) * ( $ x1 - $ x2 ) + ( $ y1 - $ y2 ) * ( $ y1 - $ y2 ) ) ; return ceil ( $ d / ( 2 * $ r ) ) ; }