PHP program to check if two circles touch each other or not .
< ? php function circle ( $ x1 , $ y1 , $ x2 , $ y2 , $ r1 , $ r2 ) { $ distSq = ( $ x1 - $ x2 ) * ( $ x1 - $ x2 ) + ( $ y1 - $ y2 ) * ( $ y1 - $ y2 ) ; $ radSumSq = ( $ r1 + $ r2 ) * ( $ r1 + $ r2 ) ; if ( $ distSq == $ radSumSq ) return 1 ; else if ( $ distSq > $ radSumSq ) return -1 ; else return 0 ; }