$a=496787459.234230497098723489;
$b=349807256234.2397823;
$c=$a+$b;
echo $c."<br>";;//350304043693.47
echo sprintf('%.20e',$c)."<br>";//3.50304043693474060059e+11
echo sprintf('%.20f',$c)."<br>";#en çok kullanılan//350304043693.47406005859375000000
echo sprintf('%.20s',$c)."<br>";//350304043693.47
echo sprintf('%e',$c)."<br>";//3.503040e+11
echo sprintf('%f',$c)."<br>";//350304043693.474060
echo sprintf('%s',$c)."<br>";//350304043693.47
echo sprintf("%10.10e", $c)."<br>";//3.5030404369e+11
echo sprintf("%10.10f", $c)."<br>";//350304043693.4740600586
echo sprintf("%10.10s", $c)."<br>";//3503040436
Bir başka örnek
$basla=microtime();
$son=microtime();
$fark=abs($basla-$son);
echo "<br>".sprintf('%.6f', $fark)." saniyede yüklendi";