Here you go, this should work:
	function isValid($varx)
	{
		$valid = true;
		$nix = array("#","(",")","<",">","?","/","\\","[","]","|");
		for($index=0;$index<strlen($varx);$index++)
		{			
			if(in_array(substr($varx,$index,1), $nix))
			{
				$valid = false;
			}
		}
		if(substr($varx, 0, 1) == " ")
		{
			$valid = false;
		}
		return $valid;
	}
$var seems to be invalid for a variable name hence the use of $varx