Expressions, only allow a certain input

Hi,

I need some help with my form.

<form action="stats.php" method="POST">

Username:<br>
<input type="text" size="25" class="form" autocomplete="off" maxlength="15" name="buxusername" value="<? echo $row["buxusername"]; ?>">
<br><br>

Account balance:<br>
$ <input type="text" size="10" class="form" autocomplete="off" maxlength="15" name="balance" value="<? echo $row["balance"]; ?>">
<br><br>

Amount of Referrals:<br>
<input type="text" size="6" class="form" autocomplete="off" size="5" maxlength="15" name="referrals" value="<? echo $row["referrals"]; ?>">
<br><br>

<font color="#9c1515">*</font> Security code:<br>
<img src="image.php" onclick="this.src='image.php?newtime=' + (new Date()).getTime();">(Click to reload)<br />
<input type="text" size="5" class="form" autocomplete="off" maxlength="5" name="code">
<br><br>

<input type="submit" value="Update">

</form>

Code (markup):

As you can see I have an input form Account Balance and Amount of Referrals.
Well, currently people can submit things like
Account Balance: lol
Amount of Referals: o_o

I want that it only allows numbers in Amount of Referrals
e.g.
Amount of Referals: 15
Amount of Referals: 15236

and in Account balance some special conditions:
e.g.
Account Balance: 10
Account Balance: 10.00
Account Balance: 10.000
Account Balance: 10.0000

Can somebody help me with this please?
Thanks in advance!!!

 

Please someone?
I can't find it!!

 

You can use functions like:

http://uk.php.net/is_int - Referral Amounts
http://uk.php.net/manual/en/function.is-numeric.php - Account balance

Jay

 

Yes it works now!
Thanks for the links

 

Ow, I have a problem again.

I use this code now to check the input of Account Balance:

function isDecimalNumber($n) {
  return (string)(float)$n === (string)$n;
}

Code (markup):

Now it only allows inputs like: 16.13 or 10, but when I try 16.1325 it doesn't work.
This is my piece of code to check if the input is correct:

if(isDecimalNumber($balance) == false){ 
$error = 1;
$errormsg .= "<b>Error</b> - Your Account Balance is not correct.";
}
if($error == 1)
{
print $errormsg."<br /><br />";

}

Code (markup):

What's wrong with my code?

 

Any chance of a Positive Rep?

Why not use is_numeric for account balance?

Jay

 

Because if I use is_numeric, it won't allow inputs like 10.5025
It needs to allow e.g. '10' or '10.50' or '10.5025' and don't allow e.g. 'lol' or '10.502575' so a maximum of 4 numbers after the point.