<?php
function xsqrt($x, $value) 
{ 
    $count = 0; 
    do{ 
        $value=$value/$x; 
        $count++; 
    }while($value>=$x); 

    return $count; 
} 
var_dump(xsqrt(2,16));
var_dump(xsqrt(2,63));
?>