Validate numbers or digits only

Hello,
I have tried to get this but...
$a=123.22;
$b="123,23";
$c="767rrrr";
$d="é45";
$e=#10;
echo (only_numbers($a))?"Valid":"Invalid";
echo (only_numbers($b))?"Valid":"Invalid";
echo (only_numbers($c))?"Valid":"Invalid";
echo (only_numbers($d))?"Valid":"Invalid";

variable $a shoud be the only one valid but it is not, it also validates $d.

function only_numbers($para)
{
if (!ereg("[a-zA-Z,]"))
{
return 1
}
}

I have also tried other things like [[:digit:]] and [0-9] but commas and letters pass through.

I just want numbers with decimal point.

how about something like

if(is_int($val) || is_float($val))
{
// it's numerical
}

or:

Thank you for trying, but none did work.

notePad's is_int-or-is_float version returns FALSE because the variables shown somehow are treated as string when queried or posted in a form.

Gipz' more elaborated version returns all data as being invalid. The pointer $this-> should be eliminated; it is not a class (I guess..)

So the function that is likely to funtion is:

The problem is that this returns TRUE even for
$para="é45"; or "[accented-letter]45"; or "4%5";
//any special and not-so-special chars out of the "alpha" range anywhere in the string (when capturing data it is received as STRING!

Is there a way to write something like...?

...all characters out of the alpha-range; including îéç#[ (special chars)...

try:

It works!!!

Zombies' function works perfectly for my case.

THNX AGAIN!