在 PHP 中设置浮点数的精度
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Set precision for a float number in PHP
提问by Mostafa Talebi
I get a number from database and this number might be either floator int.
I need to set the decimal precision of the number to 3, which makes the number not longer than (regarding decimals) 5.020or 1518845.756.
我从数据库中得到一个数字，这个数字可能是float或int。
我需要将数字的小数精度设置为3，这使得数字不长于（关于小数）5.020或1518845.756。
Using PHP
使用 PHP
round($number, $precision)
I see a problem:
我看到一个问题：
It rounds the number. I need a function to only cut the decimals short, without changing their values which round( )seems not to follow.
它对数字进行四舍五入。我需要一个函数来只截短小数，而不改变它们round( )似乎不遵循的值。
回答by Amal Murali
You can use number_format()to achieve this:
您可以使用以下方法number_format()来实现：
echo number_format((float) $number, $precision, '.', '');
This would convert 1518845.756789to 1518845.757.
这将转换1518845.756789为1518845.757.
But if you just want to cut off the number of decimal places short to 3, and notround, then you can do the following:
但是，如果您只想将小数位数缩短为 3，而不是round，那么您可以执行以下操作：
$number = intval($number * ($p = pow(10, $precision))) / $p;
It may look intimidating at first, but the concept is really simple. You have a number, you multiply it by 103(it becomes 1518845756.789), cast it to an integer so everything after the 3 decimal places is removed (becomes 1518845756), and then divide the result by 103(becomes 1518845.756).
乍一看可能有点吓人，但概念其实很简单。您有一个数字，将其乘以 10 3（变为1518845756.789），将其转换为整数，以便删除小数点后 3 位后的所有内容（变为1518845756），然后将结果除以 10 3（变为1518845.756）。
回答by georgecj11
Its sound like floorwith decimals. So you can try something like
它听起来像floor小数。所以你可以尝试类似的东西
floor($number*1000)/1000
回答by Uours
If I understand correctly, you would not want rounding to occur and you would want the precision to be 3.
如果我理解正确，您不会希望发生四舍五入，并且您希望精度为 3。
So the idea is to use number_format()for a precision of 4 and then remove the last digit:
所以这个想法是使用number_format()4 的精度，然后删除最后一个数字：
$number = '1518845.756789';
$precision = 3;
echo substr(number_format($number, $precision+1, '.', ''), 0, -1);
Will display:
将显示：
1518845.756
rather than:
而不是：
1518845.757
Links : number_format(), substr()
回答by Derezzed
See this answerfor more details.
有关更多详细信息，请参阅此答案。
function numberPrecision($number, $decimals = 0)
{
$negation = ($number < 0) ? (-1) : 1;
$coefficient = pow(10, $decimals);
return $negation * floor((string)(abs($number) * $coefficient)) / $coefficient;
}
回答by Pavla
$num=5.1239;
$testnum=intval($num*1000)/1000;
echo $testnum; //return 5.123
