blocks|key|5074528|text|function+dec2sat($decimal)
{
++++return+$decimal+*+(10+**+8)+.+'';
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|5074529|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>function dec2sat($decimal)
{
 return $decimal * (10 ** 8) . '';
}
</code></pre>

blocks|key|5212526|text|您正在尝试比较float和integer。在这种情况下，PHP需要显式地将浮点数转换为整数。当您运行以下代码时：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5212527|var_dump((int)dec2sat(0.06999206));+//+6999205|code-block|syntax|javascript|5212528|你会得到6999205，显然比6999206要小。|5212529|当你尝试比较字符串和整型时也是一样的。这将输出true：|5212530|var_dump('string'+==+0);+//+true|5212531|这是您需要始终比较类型和值的方法，以避免这种行为。下面的代码将输出true，它不是一些漂亮的解决方案，但它是有效的。也可以尝试其他情况。|5212532|var_dump(round(dec2sat(0.06999206),+0)+>=+6999206);+//+true|5212533|5212534|为什么会发生这种情况：|blockquote|5212535|5212536|5212537|浮点数的精度是有限的。虽然它取决于系统，但PHP通常使用IEEE+754双精度格式，由于舍入在1.11e-16的数量级，该格式将产生最大相对误差。非初等算术运算可能会产生更大的误差，当然，当几个运算组合在一起时，必须考虑误差传播。|5212538|此外，在基数10中可以精确表示为浮点数的有理数，如0.1或0.7，在内部使用的基数2中没有精确的浮点数表示，无论尾数的大小如何。因此，它们不能在没有小的精度损失的情况下转换成它们的内部二进制对应物。这可能会导致混乱的结果:例如，floor((0.1%2B0.7)*10)通常会返回7，而不是预期的8，因为内部表示将类似于7.9999999999999991118...|5212539|在我们的例子中，当你去掉小数点后面的所有隐藏数字时，你会得到下一个结果：|5212540|var_dump(number_format(dec2sat(0.06999206),+30,+'.',+''));+//+6999205.999999999068677425384521484375
var_dump(number_format(dec2sat(0.06999206),+9,+'.',+''));+//+6999205.999999999
var_dump(number_format(dec2sat(0.06999206),+8,+'.',+''));+//+6999206.00000000|5212541|5212542|结论：|5212543|5212544|5212545|切勿将浮点数结果信任到最后一位数，也不要直接比较浮点数是否相等。如果需要更高的精度，可以使用任意精度的数学函数和gmp函数。|5212546|要么将返回值转换为整数，要么将其向上舍入到8位小数。|5212547|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1F|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1G|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1H|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|1I|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|1J|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|1K|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|1L|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]|$1|R|3|S|5|T|7|1N|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1P|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1R|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1S|8|@]|9|@]|A|$]]|$1|12|3|13|5|D|7|1T|8|@]|9|@]|A|$E|F]]|$1|14|3|-4|5|6|7|1U|8|@]|9|@]|A|$]]|$1|15|3|16|5|T|7|1V|8|@]|9|@]|A|$]]|$1|17|3|-4|5|6|7|1W|8|@]|9|@]|A|$]]|$1|18|3|-4|5|6|7|1X|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|1B|3|1C|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|1D|3|-4|5|6|7|20|8|@]|9|@]|A|$]]]|1E|$]]

You're trying to compare float against integer. In that case PHP needs to explicitly convert float to integer. When you run code below:

<pre><code>var_dump((int)dec2sat(0.06999206)); // 6999205
</code></pre>

you will get number 6999205 which is obviously less then 6999206.

Same thing is when you try to compare string vs integer. This will output true:

<pre><code>var_dump('string' == 0); // true
</code></pre>

This is way you need always to compare type and value, to avoid this kind of behavior. Code below will output true, it is not some beautiful solution but it works. Try with other cases as well.

<pre><code>var_dump(round(dec2sat(0.06999206), 0) &gt;= 6999206); // true
</code></pre>

<blockquote>
 WHY THIS HAPPENS:
</blockquote>

Floating point numbers have limited precision. Although it depends on the system, PHP typically uses the IEEE 754 double precision format, which will give a maximum relative error due to rounding in the order of 1.11e-16. Non elementary arithmetic operations may give larger errors, and, of course, error propagation must be considered when several operations are compounded. 

Additionally, rational numbers that are exactly representable as floating point numbers in base 10, like 0.1 or 0.7, do not have an exact representation as floating point numbers in base 2, which is used internally, no matter the size of the mantissa. Hence, they cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9999999999999991118.... 

In our case when you strip all hidden digits behind decimal dot you will get next results:

<pre><code>var_dump(number_format(dec2sat(0.06999206), 30, '.', '')); // 6999205.999999999068677425384521484375
var_dump(number_format(dec2sat(0.06999206), 9, '.', '')); // 6999205.999999999
var_dump(number_format(dec2sat(0.06999206), 8, '.', '')); // 6999206.00000000
</code></pre>

<blockquote>
 CONCLUSION:
</blockquote>

Never trust floating number results to the last digit, and do not compare floating point numbers directly for equality. If higher precision is necessary, the arbitrary precision math functions and gmp functions are available. 

Either convert your returned value to integer or round it up to 8 decimal places.

blocks|key|5212560|text|我想说的第一件事是:非常感谢您花时间寻找我的问题的解决方案。我的问题的主要目的不是找出解决方案，我需要知道导致上述意外结果的原因，因为这有助于我避免以后重复。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5212561|在看了Aleksandar+Raki的答案后，我在ć中做了一些关于浮点型的搜索，现在，我想我已经找到了导致var_dump(dec2sat(0.06999206)+>=+6999206);返回FALSE的原因。你可以在这里阅读：Warning:+Floating+point+precision|offset|length|style|CODE|5212562|我认为数字0.06999206不是真正的0.06999206，它在内部存储时可能是0.069992059999...，函数dec2sat(0.06999206)的结果是6999205.999...这就是为什么Aleksandar+Rakić的解决方案返回预期结果的原因。|5212563|以下是编辑后的dec2sat()|5212564|function+dec2sat(+$decimal+)
{
+++++return+intval(round(+$decimal+*+(10**8)+));+//+$decimal+always+has+decimal+value+<=+8+digits
}|code-block|syntax|javascript|5212565|函数dec2sat()的主要目标是将floating+point+number转换为int，以避免在我的应用程序中直接处理floating+point+number。|5212566|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/language.types.float.php^0|0|1H|15|2O|5|36|X|0|0|5|A|K|A|15|H|1P|J|2C|E|0|7|9|0|0|2|9|I|L|16|3|1P|L|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@$D|12|E|13|F|G]|$D|14|E|15|F|G]]|9|@$D|16|E|17|1|18]]|A|$]]|$1|H|3|I|5|6|7|19|8|@$D|1A|E|1B|F|G]|$D|1C|E|1D|F|G]|$D|1E|E|1F|F|G]|$D|1G|E|1H|F|G]|$D|1I|E|1J|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1K|8|@$D|1L|E|1M|F|G]]|9|@]|A|$]]|$1|L|3|M|5|N|7|1N|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1O|8|@$D|1P|E|1Q|F|G]|$D|1R|E|1S|F|G]|$D|1T|E|1U|F|G]|$D|1V|E|1W|F|G]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1X|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

The first thing I want to say is: Thank you very much for spending your time to find out the solutions for my question. The main goal for my question is not to find out the solution, I need to know the reason which causes above unexpected result because it helps me avoid repeating later. 
After taking a look at the answer of Aleksandar Rakić, I did some search about float type in PHP and now, I think I have found the reason cause <code>var_dump(dec2sat(0.06999206) &gt;= 6999206);</code> return <code>FALSE</code>. You can read here: <a href="http://php.net/manual/en/language.types.float.php" rel="nofollow noreferrer">Warning: Floating point precision</a>

I think the number <code>0.06999206</code> is not really <code>0.06999206</code>, it may be <code>0.069992059999...</code> when storing internally and the function <code>dec2sat(0.06999206)</code> results in <code>6999205.999...</code> This is why the solution of Aleksandar Rakić return expected result. 

Here is the edited <code>dec2sat()</code>

<pre><code>function dec2sat( $decimal )
{
 return intval(round( $decimal * (10**8) )); // $decimal always has decimal value &lt;= 8 digits
}
</code></pre>

The main goal of the function <code>dec2sat()</code> is to convert <code>floating point number</code> to <code>int</code> to avoid processing <code>floating point number</code> directly in my app.

<pre><code>function dec2sat( $decimal )
{
 return $decimal * (10**8);
}

echo dec2sat(0.06999206); // result: 6999206 (float type)

var_dump(dec2sat(0.06999206) &gt;= 6999206); // result: FALSE
</code></pre>

Could everyone please explain to me why <code>var_dump(dec2sat(0.06999206) &gt;= 6999206);</code> return FALSE?

Tested: PHP 7.2.12, PHP 7.1.22, PHP 5.6.38

PHP bug or what am I wrong?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

function dec2sat( $decimal ){    return $decimal * (10**8);}echo dec2sat(0.06999206); // result: 6999206 (float type)var_dump(dec2sat(0.06999206) >= 6999206); /...

问PHP错误或者我哪里错了？
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问PHP错误或者我哪里错了？EN