php保留2位小數，只舍不入

<?php

/**

 * 小數保留後2位，只舍不入

 */

function round_num($num){

if($len = strpos($num,'.')){

$dian_num = substr($num,$len+1,$len+3);//獲取小數點後面的數字

if(strlen($dian_num) >= 2){//判斷小數點後面的數字長度是否大於2

$new_num = substr($num,0,$len+3);

}else{//補0

$new_num = $num.'0';

}

}else{//補.00

$new_num = $num.'.00';

}

return $new_num;

}

$num = 20.1111;

echo round_num($num);

?>