PHP simple interest

jus71n742 · 04-15-2008, 02:16 PM

I am playing with PHP trying to get any 3 inputs from the user and then compute the simple interest from what that person puts in. I have so far the following

php code:

Code:

<?php
$var_r=$_POST['r'];
echo $var_r . "\n";
$var_P=$_POST['P'];
echo $var_P . "\n";
$var_t=$_POST['t'];
echo $var_t . "\n";
$var_I=$_POST['I'];
echo $var_I

if (!($var_I=$_POST['I']))
{
	$var_m=$var_P * $var_t * $var_r;
}
elseif (!($var_P=$POST['P']))
{
	$var_m=$var_I/($var_r*$var_t);
}
elseif (!($var_t=$POST['t']))
{
	$var_m=$var_I/($var_p*$var_r);
}
else (!($var_r=$POST['r'}))
{
	$var_m=float=2(($var_I/($var_p*$var_t))*100);

?>

your simple interest will be:<?php echo $var_m ; ?>

basically I am trying to either set up a loop of an if statement stating that if (3 variables are input) do this formula and so on and so forth....any help getting going would be much appreciated.

BrianK · 04-15-2008, 04:36 PM

so what's the question? are you asking for a better method? or are you asking for the form that would submit these values? something else? There are a few typos in there & you should probably check more than one variable at a time using the && operator.

Maz_ · 04-15-2008, 04:38 PM

Code:

<?php

if(isset($_POST['r'])&&isset($_POST['P'])&&isset($_POST['t'])&&isset($_POST['I']))
{
    .
    .
    .
    .
}

or use foreach
( http://fi.php.net/foreach )

graemef · 04-15-2008, 06:31 PM

The function that you want is empty(). This will return true is the value is empty.

You will of course want to check that you have three valid values, you can do this by stepping through each variable and keeping a count of the number of number of non-empty once, so long as you have a total of three then you have valid input and so you can proceed.

Give it a go and if you have any problems get back.

jus71n742 · 04-16-2008, 10:21 AM

where is this function empty? a tutorial maybe somewhere?....I have heard of this function but I haven't found much on it. how would you set that up?

BrianK · 04-16-2008, 11:59 AM

Quote:

Originally Posted by jus71n742

where is this function empty? a tutorial maybe somewhere?....I have heard of this function but I haven't found much on it. how would you set that up?

http://www.php.net/

use the "search for" fucntion on that site. Every php function is there.

Wim Sturkenboom · 04-16-2008, 01:02 PM

@BrianK
If one knows the function name (as in this case), one does not need to search but can append it at the end of the URL (in this case http://www.php.net/empty).

Better even, if you do NOT know the exact function name, just add it like in http://www.php.net/mysql_affectedrows . It will tell you that it could not find it and give you a list of names that are close.

Hasn't failed me yet but might only be possible for english language.

graemef · 04-16-2008, 05:32 PM

Quote:

Originally Posted by jus71n742

where is this function empty? a tutorial maybe somewhere?....I have heard of this function but I haven't found much on it. how would you set that up?

As others have mentioned you can look up the details of empty() in the php manual, either the online version or if you have a local copy you can find it there.

Technically empty() is not a function but a construct of the language, but because it follows the syntax of a function lazy people like me call it a function. However because of this it does have some limitations all explained in the manual.

Finally, like many modern scripting languages (Perl, Python, Ruby and PHP all come to mind) are supported by a large collection of functions that are considered part of the language and are bundled by default with the language and yet more can be added as you need them. So a large part of learning the language is in understanding the functions that are available. My advice, once you are comfortable with the core language browse the manual just looking at the wide collection of function families that are available and then spend a little time looking at the function families that look useful or intriguing. An early investment in the array and string functions would be time well spent.

Enjoy the journey

jus71n742 · 04-17-2008, 01:59 PM

Code:

if empty($var_I==NULL])

{

	$var_I=$var_m;

	$var_m=$var_P * $var_t * $var_r;

}

elseif empty($var_P==NULL)

{

	$var_P=$var_m;

	$var_m=$var_I/($var_r*$var_t);

}

elseif empty($var_t==NULL)

{

	$var_t=$var_m;

	$var_m=$var_I/($var_p*$var_r);

}

else empty($var_r==NULL)

{

	$var_r=$var_m;

	$var_m=float=2(($var_I/($var_p*$var_t))*100);



?>

is this more along the lines of what you are talking about

graemef · 04-17-2008, 04:32 PM

Try

Code:

if (!empty($var_I))

BrianK · 04-17-2008, 04:37 PM

Quote:

Originally Posted by jus71n742

Code:

if empty($var_I==NULL])

is this more along the lines of what you are talking about

the expression ($var_I==NULL) returns a true or false.

Therefore "empty($var_I==NULL)" expands to empty(true) or empty(false) which makes no sense.

as graemef said, the correct usage is empty(<variable>) or, in this case empty($var_I)

marquardl · 04-18-2008, 03:23 PM

PHP also has the possibility to sort out invalid return values for parameters where NULL is a possible value.

$number == NULL // $number is a number and can be 0
$number === NULL // $number is not set or is FALSE

GWN

jus71n742 · 04-20-2008, 10:35 PM

Quote:

Originally Posted by graemef

Try

Code:

if (!empty($var_I))

that was the first thing I tried...i kept getting a parse error on line 29 which is the start of the if statements on mine

graemef · 04-21-2008, 05:45 AM

If you are getting a parse error on stmt 29, then it could be an error on line 28.

What exactly is the error?

jus71n742 · 04-21-2008, 10:15 AM

Ok I thought I was done...apparently not...I am still getting an error and I had some help with it. we wrote the code together then I copied it EXACTLY like it was on his when it worked....now that it is on my machine ....

Quote:

parse error, unexpected T_VARIABLE on line 28

I have no clue what is wrong. I am probably looking right at it and not seeing it..
here is line 29 up to the start of the actual PHP

Code:

<?php
echo "RATE:".$_POST['r']."<br>";
echo "PRINCIPLE: ".$_POST['P']."<br>";
echo "TIME: ".$_POST['t']."<br>";
echo "INTEREST:".$_POST['I'] ."<br>";

$r = $_POST['r'];
$p = $_POST['P'];
$t = $_POST['t'];
$i = $_POST['I'];

if (empty($i)) {
    $i = $p * $t * $r;
    print ("Interest will be: ").$i;