PHP function for Digits Grouping in indian format

<?php 
function convertit($num){ 
    $pos = strpos($num, ".");
    if ($pos !== false) {
        $ps = substr($num,-2);
    	$num = substr($num,0,-3);    
    } else {
	    $ps = "00";
	}    
    if(strlen($num)>3){ 
            $lastthree = substr($num, strlen($num)-3, strlen($num)); 
            $restunits = substr($num, 0, strlen($num)-3); 
            $restunits = (strlen($restunits)%2 == 1)?"0".$restunits:$restunits;
 
            $expunit = str_split($restunits, 2); 
            for($i=0; $i<sizeof($expunit); $i++){ 
                $explrestunits .= (int)$expunit[$i].",";
            }    
 
            $thecash = $explrestunits.$lastthree; 
    } else { 
           $thecash = $convertnum; 
    } 
 
    return $thecash.".".$ps;
}    
?>