php validation prevents entering 0 as a value?

Question

I have a field in a form for entering the number of masters titles won by a Tennis player. Some players have 0 titles. Even though my validation checks for an empty field I cannot enter 0. What changes do I need to make to allow 0 to be entered?

if (empty($_POST["masters"])) {
    $has_errors = true;
    $mastersErr = "Enter 0-10";
} else {
    $masters = validate_input($_POST["masters"]);
}

Answer 1

use if ($_POST["masters"] === '') { to check for empty string

this is because

empty($variable) returns true if $variable equals false, null, '' (empty string) or 0

you can't use $_POST['masters'] == '' because in PHP statement 0 == '' is true

you have to use === operator

please also mind $_POST['xxx'] === 0 will never work because values in $_POST are strings

---

Anyway if you want user to put number between 0-10 I would suggest to do this check

if(is_numeric($var) && ($var >= 0) && ($var <= 10) && (intval($var) == $var))
{
    // OK
}else
{
   // not OK
}

This is because space character will pass $_POST["masters"] === '' check.

In validation you should always create if statements keeping in mind to check "is this value OK", not "is this value bad". For example if you want to validate email you dont' check "is value empty" "is value a number" "is value a float", you check "is value a email"|

is_numeric() is good, because

• is_numeric('') is false
• is_numeric(' ') is false
• is_numeric(0) is true

but beware! because

• is_numeric('0.1') is also true...

...so you need another check:

(intval($var) == $var) - this is how you make sure user entered integer (not float) number

PHP Manual:

• http://www.php.net/manual/en/language.operators.comparison.php
• http://www.php.net/is_numeric
• http://www.php.net/intval