PHP: Best way to check if input is a valid number?

Question

What is the best way of checking if input is numeric?

• 1-
• +111+
• 5xf
• 0xf

Those kind of numbers should not be valid. Only numbers like: 123, 012 (12), positive numbers should be valid. This is mye current code:

$num = (int) $val;
if (
    preg_match('/^d+$/', $num)
    &&
    strval(intval($num)) == strval($num)
    )
{
    return true;
}
else
{
    return false;
}

Answer 1

ctype_digit was built precisely for this purpose.