7
0
32
47534

asdf
35/gdf
../34.

etc..

if (preg_match("/^[0-9]$/", $original_stock))
{
    $error .="Original stock must be numerical.";
}

/^d+$/

/^d+.?d*$/

#Assuming $original_stock is a single value...
if (is_int($original_stock)) {
    #Valid, do stuff
}
else {
    #Invalid, do stuff
}

#Assuming $original_stock is an array...
$valid = true;
foreach ($original_stock as $s) {
    if (!is_int($s)) {
        $valid = false;
        break;
    }
}
if ($valid) {...}
else {...}

/^[0-9]+$/

/^d+$/

/^d+(.d{1,2})?/

if (!preg_match("/^+$/", $original_stock)) {
  // error
}

is_int

/^[0-9]$/

function validate_int($subject)
{
    //Pattern is numbers
    //if it matches anything but numbers, we want a fail
    $pattern = '/[^0-9]/';
    $matches = preg_match($pattern, $subject);
    if($matches > 0)
      return false;
    else
      return true;
  }

if (ctype_digit($x) && $x > 0) {
    // here you go
}