Description:
------------
The problem occurs in version 5.3.4, the same situation does not create problems in version 5.2.6.

Passing an empty string as a parameter is generated an error that the parameter must be of type double the problem does not occur if the same string is not empty.

Test script:
---------------
Example 01:
Code: 
<?
 $x = "";
 echo "-->". number_format($x);
?>

Output:
Warning: number_format() expects parameter 1 to be double, string given in /www/htdocs/test.php on line 5
-->

Example 02:
<?
 $x = "0";
 echo "-->". number_format($x);
?>

Output:
-->0

Expected result:
----------------
I hope the developers look fondly and fix this problem. Although trivial, many other applications users can also get this problem.