[RESOLVED] Multiplicaton?

BuzzStPoint

I have 2 Input fields. that get posted to the database.

How can I minus (-) these 2 tables and display it on my page..?

For example,
Table Alkalinity
Table Alk_Needs

If a user puts in 40 for the Alkalinity and the Alk_needs is filled in at 130
How can I minus that to display at result?

BuzzStPoint

Got it...

I was forgetting a ;
It works now.

Weedpacket

That's a relief, because it's one of the worst questions I've seen posted in a while. I for one wouldn't have had the foggiest idea what you were talking about.

scrupul0us

^what he said....

I know you're a new guy Buzz but your thread title indicates multiplication but your question is regarding subtraction... coupled with no code to look at and you get yourself one lousy thread

For the future, if you title your threads accurately and provide code/errors/etc in your post the community will be more able/willing to assist you

Welcome =)

BuzzStPoint

Sorry, I was posting and working at the same time..

The here's what I was trying to accomplish.
The only tables that would have user input would be:
Alkalinity
Alk_Needs
Calcium
Cal_Needs

Then I just did the math

// Alkalinity Calculations =SUM(H40/10*0.075*1.5*16) (Excel)
$Alk_Change  = $Alk_Needs - $Alkalinity;
$Alk_Add_oz  = (((($Alk_Change / 10) * 0.075) * 1.5) * 16);
$Alk_Add_lbs = $Alk_Add_oz /16; 
//Calcium Calculations =SUM(M40/10*0.075*1.25*16)
$Cal_Change  = $Cal_Needs - $Calcium;
$Cal_Add_oz  = (((($Cal_Change / 10) * 0.075) * 1.25) * 16);
$Cal_Add_lbs = $Cal_Add_oz /16;

It wasn't working for me. No errors. The php echo wasn't displaying my math. When I posted the rest of the thread I was on the beginning part of the equation where I needed to subtract.
But once I put in the ; the codes started working for me.. I have it displaying now.

scrupul0us

when developing code, you can add:

ini_set('error_reporting', E_ALL);
ini_set('display_errors', 1);

to the top of your page to ensure all errors/warnings are output to the browser

NogDog

scrupul0us;10934232 wrote:
when developing code, you can add:
ini_set('error_reporting', E_ALL);
ini_set('display_errors', 1);
to the top of your page to ensure all errors/warnings are output to the browser

True, though if the problem was a missing ";" it was probably a parse error, which would be thrown before that code gets processed, and thus not displayed if the system settings have display_errors turned off. That's where an editor/IDE with built-in syntax checking can be a real time-saver.

BuzzStPoint

I do have another small question with the php math and numbers.

$Free_Chl = $R0871_drops * 0.2;
$Comb_Chl = $R0003_drops * 0.2;
$Breakpoint = $Comb_Chl * 10;
$AmtShk_oz = ((13 * 0.075) * $Breakpoint); //=SUM(13*0.075*T39)
$AmtShk_gal = $AmtShk_oz / 128;

R0871_drops & R0003_drops are database tables.
All the formulas are working correctly.
But when I do my <?php echo $AmtShk_gal ?> it displays the value as needed. Depending on the drops you entered. the value will be different. But it shows up as: 0.03046875
Is there a way I can make is shorter? Like 0.03 ? No rounding, just drop off the rest of the numbers.

NogDog

If you don't want it to round, best I can think of at the moment is:

<?php
$number = round(floor($number * 100) / 100, 2);

(The round() is in there just in case you get any extra decimal points due to floating point precision errors in the division operation.)

Weedpacket

NogDog wrote:
if the system settings have display_errors turned off. That's where an editor/IDE with built-in syntax checking can be a real time-saver.

That's where a dev system in which that setting is turned on can be a real time saver!

BuzzStPoint

The ini-set was a real help. I had 4 errors on the page that sped up my trouble shooting,

As for the number setting..
After some trial and error, I finally got it to work.. It still rounds, But when you are dealing with less then a gallon. This field doesn't need to be real accutate. This is why I also have ounces as well.
In my html tables. I had this:

    <td class="main2"><?php echo $AmtShk_gal ?></td>

I changed the echo to this

    <td class="main2"><?php echo" ".number_format($AmtShk_gal,2); ?></td>