Reverse long PHP if function for number calculation - php

Question

I'm making application for recording and processing company leave records using PHP and mysql. In my application I have to process three main leave type as below with their respective counts.
causal - 7
annual - 14
medical - 7
In my database I have table called leaves and it contian those three columns and their values respectively as follows
---name----casual----annual----medical
---jhon------7---------14--------7---
---mary------7---------14--------7---
---bill------5----------3--------0---
when employee applying a leave PHP function check available leave counts and subtract applied leave number from those three values like this
if leave type is casual and leave count is 15 it should be subtract both casual, medical and annual leaves to fulfill the employees leave requirement.I managed to implement up to this part. below is my code
if ($ltype == "medical")
{
if ($medical >= $hmd)
{
$medical-= $hmd;
}
else
{
$tval = $hmd - $medical;
$tval2 = $hmd - $tval;
$medical-= $tval2;
if ($casual >= $tval && $tval > 0)
{
$casual-= $tval;
}
else
{
$tval3 = $tval - $casual;
$tval4 = $tval - $tval3;
$casual-= $tval4;
if ($annual >= $tval3 && $tval3 > 0)
{
$annual-= $tval3;
}
else
{
$tval5 = $tval3 - $annual;
$tval6 = $tval3 - $tval5;
$annual-= $tval6;
$nopay += $tval5;
}
}
}
}
I have three code sets for three leave types and above code do the math as what I want. But my problem is when sometime users want to re-add those subtracted leave to the leave table. when comes to this I have to calculate this function reverse for get the exact numbers subtracted by each column form the first function. then I planned to calculate add how many leaves subtracted by each columns to the end of the leave record. but when reversing this also not working since those records not process as any order.
I want to implement way to re-add those leaves to the leaves table without any error.
I know my method may not suitable for this type of problem and this is extremely basic programming question. could someone please explain me how do I revers my first function exactly as the same or is there any other programming concepts that should I follow for solve these type of problems.

Answer 1

Okay, well assuming $hmd is number of days...this should get you very close:
http://sandbox.onlinephpfunctions.com/code/f16d899de4318a89e1d80e8737c49b079a5ee179
<?php
$ltype = 'medical';
$casual = 7;
$annual = 15;
$medical = 7;
$nopay = 0;
$hmd = 9;
echo "medical $medical, casual $casual, annual $annual, nopay $nopay\n";
if ($ltype == "medical") {
if ($medical >= $hmd) {
$medical -= $hmd;
} else {
// sorry no more med leave
$rem = $hmd - $medical;
$medical = 0;
if ($casual >= $rem && $rem > 0) {
$casual -= $rem;
} else {
// sorry no more cas leave
$rem2 = $rem - $casual;
$casual = 0;
if ($annual >= $rem2 && $rem2 > 0) {
$annual -= $rem2;
} else {
// sorry now you owe us money
$nopay += ($rem2 - $annual);
$annual = 0;
}
}
}
}
echo "medical $medical, casual $casual, annual $annual, nopay $nopay\n";
// need to set these to know when to "roll" to the next leave type...
$max_casual = 7;
$max_annual = 15;
$max_medical = 7;
if ($ltype == "medical") {
$rem = 0; // remainder after paying back nopay
if ($nopay >= $hmd) {
$nopay -= $hmd;
// well, we put some back but you still owe us!
} else {
// alright you paid it back!
$rem = $hmd - $nopay;
$nopay = 0;
}
if ($rem > 0) {
// let's restore some annual
$annual += $rem;
if ($annual > $max_annual) {
$rem = $annual - $max_annual;
$annual = $max_annual;
} else {
$rem = 0;
}
}
if ($rem > 0) {
// let's restore some casual
$casual += $rem;
if ($casual > $max_casual) {
$rem = $casual - $max_casual;
$casual = $max_casual;
} else {
$rem = 0;
}
}
if ($rem > 0) {
// whoa you're rolling in days off
$medical += $rem;
if ($medical > $max_medical) {
$rem_not_possible = $medical - $max_medical;
$medical = $max_medical;
} else {
$rem = 0;
}
}
}
echo "medical $medical, casual $casual, annual $annual, nopay $nopay\n";