php fooat 数运算 html中的现实结果

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php 代码例子：

<?php$a = 3.01;$b = 3;$c = 152.79;$d = 152;$e = 152.09;$f = 152;$g = 217.99;$h = 217;$i = 217.38;$j = 217;?><div>    <ul>        <li>        <?php             $bb = $a - $b;            $aa = round($bb,2);             echo "round( 3.01 - 3 , 2 ) = ".$aa;        ?>        </li>        <li>        <?php             echo "3.01 - 3 = ".($a - $b);        ?>        </li>    </ul></div><div>    <ul>        <li>        <?php             $cc = $c - $d;            $dd = round($cc,2);             echo "round( 152.79 - 152 , 2 ) = ".$dd;        ?>        </li>        <li>        <?php             echo "152.79 - 152  = ".($c - $d);         ?>        </li>    </ul></div><div>    <ul>        <li>        <?php             $ee = $e - $f;            $ff = round($ee,2);             echo "round( 152.09 - 152 , 2 ) = ".$ff;        ?>        </li>        <li>        <?php             echo "152.09 - 152 = ".($e - $f);         ?>        </li>    </ul></div><div>    <ul>        <li>        <?php             $gg = $g - $h;            $hh = round($gg,2);             echo "round( 217.99 - 217 , 2 ) = ".$hh;        ?>        </li>        <li>        <?php             echo "217.99 - 217 = ".($g - $h);         ?>        </li>    </ul></div><div>    <ul>        <li>        <?php             $ii = $i - $j;            $jj = round($ii,2);             echo "round( 217.38 - 217 , 2 ) = ".$jj;        ?>        </li>        <li>        <?php             echo "217.38 - 217 = ".($i - $j);         ?>        </li>    </ul></div>

输出的结果内容：

round( 3.01 - 3 , 2 ) = 0.01
3.01 - 3 = 0.0099999999999998

round( 152.79 - 152 , 2 ) = 0.79
152.79 - 152 = 0.78999999999999

round( 152.09 - 152 , 2 ) = 0.09
152.09 - 152 = 0.090000000000003

round( 217.99 - 217 , 2 ) = 0.99
217.99 - 217 = 0.99000000000001

round( 217.38 - 217 , 2 ) = 0.38
217.38 - 217 = 0.38

值在临近0.01 和 0.09 的时候会出现莫名其妙的内容。

一定要做好值的数量截取（位数的准确）

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