Calculation from a table

jsp

Help!

I would like to be able to pull many calculation's from a database field and have it done in PHP. These calc's can change on the fly and I will setup a screen so the user can change them. I have not had luck getting the calculation to work.

Here is a small example:
First I place a list of numbers into an array. (works great)

next I pull the Calculation field from the table
$calc = ($fld[47]/24)

do the eval command
eval ("\$calc = \"$calc\";"); echo displays 677126/24

All looks good but at this point the system is looking at the
"677126/24" as a string not as a calculation. I'm not sure what command I can use so the system looks at this commad as a calculation not a string.

Please let me know if you need more information or have any ideas.

Thanks,
jsp

tomhath

Think about what the eval function is seeing:

$calc="677126/24";

You shouldn't have those quotes.

jsp

I understand what the function is seeing that is why I'm asking the question. I want to be able to store calculation's inside a field in a table (ex. ($fld[42]/24)) The eval command does not do the calculation. I was wondering if anyone has any ideas of any other commands that would do this.

The calculations can change from week to week and I would like to be able to pull them from a table.

Thanks for the input,
jsp

Weedpacket

tomhath has already explained what the problem is and what to do about it.

jsp

Maybe I am not explaining myself clearly. I'll attempt one more time.

I want to pull the calculation's in from a table.

$fld[] is setup as an array containing numbers for the calculations.

I would like to pull the calculations from a table. What is stored in the field in a table.
Examples: ($fld[42]/24)
($fld[45]/$fld[57])/$fld[50]

when using the eval command I get:
677126/24
(10/5)/2

I am not manually setting up the calculations as a string the system is seeing them that way because they come from the table.

Does anyone know of anyway to get this to work?

Weedpacket

You've already said exactly what the problem is: "the system is looking at the '677126/24' as a string not as a calculation".

tomhath has said exactly why it's looking at it as a string - the extra quotes you're explicitly putting around $calc it makes it so:

Think about what the eval function is seeing:
$calc="677126/24";
You shouldn't have those quotes.

So don't put those quotes in.
Trust me.
It works.

jsp

Again, Thanks for the input.

No where in my code do I have the line:

$calc="677126/24";

I have been using php for awhile and have done many calc's.

What I am doing is trying to pull the calculation from a field in a table, as I've stated before. In the table I store: ($fld[42]/24)
after doing this command
eval ("\$calc = \"$calc\";");

This is when the system see's $calc as being a string of 677126/24.

I am going to look into other design options.

Thank you for your time!