algorithm - How to round down to the nearest significant figure in php -

is there slick way round down nearest significant figure in php?

so:

0->0 9->9 10->10 17->10 77->70 114->100 745->700 1200->1000 

?

$numbers = array(1, 9, 14, 53, 112, 725, 1001, 1200); foreach($numbers $number) {     printf('%d => %d'             , $number             , $number - $number % pow(10, floor(log10($number)))             );     echo "\n"; } 

unfortunately fails horribly when $number 0, produce expected result positive integers. , math-only solution.