verifying numeric input

[Enlightened]

hello i need to verify numeric input in dollar amount, My problem is i made a regex for it and someone told me im better off using number format, But what ive made does not restrict it to proper format, Here is what ive had both times.

$number = $_POST['amount'];
$amount = number_format($number, 2, '.', '');
if(isset($amount) && (!empty($amount)) && strlen($amount) < 4 ||   strlen($amount) > 9)
{
	$errors[] = "The payment amount entered must be in proper format. (i.e 100.00, 40.00)";
	}else{
	$amt = trim($_POST['amount']);

and

<?php 

if(!eregi('^[1-9]{2,3},|\.[0-9]{2,3}\.[0-9]{2}', stripslashes(trim($_POST['amount']) ) ) ) 

{ 

$problem = TRUE; 

} 
if(!$problem) 
{ 
echo 'Thank you.'; 
}else{ 

echo 'Please go back and enter a proper ammount 
} 

?>

Can anyone suggest a better way (or at least one that might work 🙂 )

[_RL_Ian]

If you want to check to see if it is a decimal (i.e. 12.50), use this:

$var = 12.50;
if (is_float($var))
{
	echo($var . " is a float");
}

//12.50 will return true
//12 will return false

Is this what you want?

[Enlightened]

Ill give it a try i just need to know if it will verify that it is a legit amount, Is that good enough to validate the users input?

[_RL_Ian]

As long as you are passing a variable that is always in 0.00 format, it should work. Just add this part to make sure that the amount is greater than 0 and it should do the trick...

<?php
if (is_float($var) AND $var > 0)
{
	echo("12.5 is a float");
}
?>

[paulnaj]

Hi, here's a really strict regex (and a little form to test it)...

<?php 
$n = isset($_GET['n'])? trim($_GET['n']): '1.23';
$regex = '/^[0-9]+\.[0-9]{2}$/'; 
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="get">
	<input type="text" name="n" value="<?php echo $n; ?>" size="10" maxlength="10">
	<input type="submit">
</form>
<br>
<?php	
if(preg_match($regex, $n)){
	echo '<strong>'.$n.'</strong> is a currency';
} else {
	echo '<strong>'.$n.'</strong> is not a currency';
}
?>

Paul. 🙂