Easy way to validate multiple fields of same content

I have multiple fields in my form and the input can only be any number from:

0 to 20

I'm trying the following without any success

function validate_qty($t) {
  $forbidden = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20');
  foreach ($forbidden as $p)
    if (strpos($t, $p) !== false) return true;
  return false;
}

Code (markup):

with this

elseif (!validate_qty($_POST['pr1'])) {
  	echo "You can only enter a number (0 to 20) in the quantity field<br>";
    echo "<a href='javascript:history.back(1);'>Click here to return</a>";
}
elseif (!validate_qty($_POST['pr2'])) {
  	echo "You can only enter a number (0 to 20) in the quantity field<br>";
    echo "<a href='javascript:history.back(1);'>Click here to return</a>";
}

Code (markup):

 

looks like you are doing a binary compare !== and declaring the array with string items. make sure you are comparing the correct datatype to datatype when using binary compare.

 

why not

function validate_qty($i){
 if((int)$i > 0 OR (int)$i <20) return true;
 return false;
}

PHP:

 

On the right track, but this will ensure a number between 0 and 20 and reject non-numeric input.

function validate_qty($i)
{
if( preg_match( '![^0-9]!', $i) ) return false;
if( $i >= 0 and $i <21) return true;

return false;
}

Code (markup):

 

Thanks clancey, works a treat.

Ian