Convert a number to a specific format : Using PHP's `[number_format()][1]` function, returns a formatted number. 

I want to convert the number to that format, not replace it. So i am trying to use a void function but the number is not converted.

The number `10500100` should be converted to : `10,500,100.00`

    <?php
    
    function format_number_($number)
    {
     $number =  number_format($number,2,'.',',');    
    }
    
    $a = 10500100;
    
    format_number_($a); 
    echo  $a;
    ?>


  [1]: https://www.php.net/manual/en/function.number-format.php