Maximum area of quadrilateral | PHP program to find maximum are of a quadrilateral ; Calculating the semi - perimeter of the given quadrilateral ; Applying Brahmagupta 's formula to  get maximum area of quadrilateral ; Driver code
< ? php function maxArea ( $ a , $ b , $ c , $ d ) { $ semiperimeter = ( $ a + $ b + $ c + $ d ) / 2 ; return sqrt ( ( $ semiperimeter - $ a ) * ( $ semiperimeter - $ b ) * ( $ semiperimeter - $ c ) * ( $ semiperimeter - $ d ) ) ; } $ a = 1 ; $ b = 2 ; $ c = 1 ; $ d = 2 ; echo ( maxArea ( $ a , $ b , $ c , $ d ) ) ; ? >