php validating a amount

Question

I have an amount field which always is going to be positive number without decimal points like 10000, 1200, 10, 40 etc. I am using the code below to check for a valid amount.

if (!preg_match('/^[1-9][0-9]*$/', $_POST['amount'])) {
    $error[] = 'Invalid amount';
}

Is it right. And, do i need to check for empty post amount using empty function of php separately or does above preg_match also checks for empty string amount.

No, you don't need to check for empty string. Your current regex forces one digit to exist. — revo, Sep 25 '18 at 10:04

fabrik · Accepted Answer · 2018-09-25T10:01:07.733

2

Why not simply use filter_var(), like:

if (!abs(filter_var($_POST['amount'], FILTER_VALIDATE_FLOAT))) {
    $error[] = 'Invalid amount';
}

edited Sep 25 '18 at 10:01

answered Sep 25 '18 at 09:46

fabrik

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Is it necessary to use intval – Kuldeep Thakur Sep 25 '18 at 09:51
1

does it also reject amount like 0010 – Kuldeep Thakur Sep 25 '18 at 09:52
@KuldeepThakur You're right, `intval()` could be enough. – fabrik Sep 25 '18 at 09:54
ok, thanks. What about a positive floating number like 10.5 – Kuldeep Thakur Sep 25 '18 at 09:57
@KuldeepThakur see my updated answer. – fabrik Sep 25 '18 at 10:01
@KuldeepThakur you stated these'll be positive numbers without decimal points. – fabrik Sep 25 '18 at 10:05
yes, these'll be positive numbers without decimal points. – Kuldeep Thakur Sep 25 '18 at 10:12
i have another field which is positive number and may or may not contain decimal point ? What about this case ? – Kuldeep Thakur Sep 25 '18 at 10:13
`FILTER_VALIDATE_FLOAT` can handle that too. Please take a look at the link provided in my answer, you can use different filters according to your use case. – fabrik Sep 25 '18 at 10:15
ok thanks. Also does i have to check for empty post variable – Kuldeep Thakur Sep 25 '18 at 10:18

score 0 · Answer 2 · answered Sep 25 '18 at 09:47

0

I would compare the string to itself when converted to the absolute int value. It is more readable and maintainable.

if ($_POST['amount'] !== abs(intval($_POST['amount']))) {
    $error[] = 'Invalid amount';
}

answered Sep 25 '18 at 09:47

Barry

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php validating a amount

2 Answers2