01.$sum = 0;
02.$difference = 0;
03.echo "<br> ค่าน้ำ = ";
04.echo $x = 40;
05.echo " หน่วย ";
06.$a1 = 10; $pire1 = 16 ;
07.$a2 = 10;$pire2 = 19 ;
08.$a3=10; $pire3 = 20;
09.$a4 =0; $pire4 =22;
10.$difference = $x - $a1;
11.if( $difference >= $a1) {
12. echo "<br> 10หน่วยแรก = ";
13. echo $sum= $sum + ($a1* $pire1);
14. echo " ";
15. echo $difference = $difference - $a2;
16.}
17.if( $difference >= $a2) {
18. echo "<br> 10หน่วยที่ 2 = ";
19. echo $sum= $sum + ($a2* $pire2);
20. echo " ";
21. echo $difference = $difference - $a3;
22.}
23.
24.if( $difference >= $a3) {
25. echo "<br>10หน่วยที่ 3 = ";
26. echo $sum= $sum + ($a3* $pire3);
27. echo " ";
28.echo $a4 = $difference;
29.}
30. echo "<br>ค่าน้ำหน่วยที่เหลือ = ";
31.echo $sum= $sum + ($a4* $pire4);
32.echo "<br>";
33.echo "ค่าน้ำทั้งหมด = "; echo $sum;
