blocks|key|1589407|text|使用constant()函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1589408|$id+=+constant("ThingIDs::$thing");|code-block|syntax|javascript|1589409|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/function.constant.php^0|2|A|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Use the <a href="http://php.net/manual/en/function.constant.php" rel="nofollow noreferrer">constant()</a> function:
<pre class="lang-php prettyprint-override"><code>$id = constant(&quot;ThingIDs::$thing&quot;);
</code></pre>

blocks|key|1803938|text|使用反射|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1803939|$r+=+new+ReflectionClass('ThingIDs');
$id+=+$r->getConstant($thing);|code-block|syntax|javascript|1803940|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use Reflection

<pre><code>$r = new ReflectionClass('ThingIDs');
$id = $r-&gt;getConstant($thing);
</code></pre>

blocks|key|1589429|text|如果使用命名空间，则应将命名空间包括在类中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1589430|echo+constant('My\Application\ThingClass::ThingConstant');+|code-block|syntax|javascript|1589431|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you are using namespaces, you should include the namespace with the class.

<pre><code>echo constant('My\Application\ThingClass::ThingConstant'); 
</code></pre>

blocks|key|1589411|text|<?php

class+Dude+{
++++const+TEST+=+'howdy';
}

function+symbol_to_value($symbol,+$class){
++++$refl+=+new+ReflectionClass($class);
++++$enum+=+$refl->getConstants();
++++return+isset($enum[$symbol])?$enum[$symbol]:false;
}

//+print+'howdy'
echo+symbol_to_value('TEST',+'Dude');|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1589412|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>&lt;?php

class Dude {
 const TEST = 'howdy';
}

function symbol_to_value($symbol, $class){
 $refl = new ReflectionClass($class);
 $enum = $refl-&gt;getConstants();
 return isset($enum[$symbol])?$enum[$symbol]:false;
}

// print 'howdy'
echo symbol_to_value('TEST', 'Dude');
</code></pre>

blocks|key|1804086|text|如果您有对类本身的引用，则可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1804087|if+(defined(get_class($course).+'::COURSES_PER_INSTANCE'))+{
+++//+class+constant+is+defined
}|code-block|syntax|javascript|1804088|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you have a reference to the class itself then you can do the following:

<pre><code>if (defined(get_class($course). '::COURSES_PER_INSTANCE')) {
 // class constant is defined
}
</code></pre>

blocks|key|1804174|text|我的问题和这个问题类似。当您有对象，但没有类名时，您可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1804175|$class_name+=+get_class($class_object);
$class_const+=+'My_Constant';

$constant_value+=+constant($class_name.'::'.$class_const);|code-block|syntax|javascript|1804176|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

My problem was similiar to this subject. When you have the object, but not the class name, you could use:

<pre><code>$class_name = get_class($class_object);
$class_const = 'My_Constant';

$constant_value = constant($class_name.'::'.$class_const);
</code></pre>

blocks|key|1589744|text|我知道我来晚了，但我希望这能帮上忙。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1589745|根据Phil的回答，我创建了一个可以扩展的默认枚举器类。|offset|length|1589746|class+DefaultEnum
{
++++static+public+function+getConstantText(string+$constant)
++++{
++++++++try+{
++++++++++++//+Get+child+class+name+that+called+this+method
++++++++++++$child_class+=+get_called_class();

++++++++++++$reflection+=+new+ReflectionClass($child_class);
++++++++++++$const+=+$reflection->getConstant($constant);

++++++++++++return+$const;
++++++++}+catch+(\ReflectionException+$e)+{
++++++++++++//+...
++++++++}
++++}
}

class+CustomEnum+extends+DefaultEnum
{
++++const+something+=+'abcd';
++++const+something2+=+'ABCD';
}|code-block|syntax|javascript|1589747|您可以像这样调用此方法|1589748|CustomEnum::getConstantText('something');|1589749|它将返回'abcd'。|style|CODE|1589750|函数get_called_class()是一个返回调用此方法的类名的函数，它专门用于静态方法。|1589751|在这种情况下，$child_class值将为CustomEnum::class。ReflectionClass接受字符串和对象作为参数。|1589752|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/283366/phil|1|https://www.php.net/manual/en/function.get-called-class.php^0|0|2|4|0|0|0|0|0|4|6|0|2|I|2|I|1|0|7|C|M|H|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@]|9|@$D|18|E|19|1|1A]]|A|$]]|$1|F|3|G|5|H|7|1B|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|1C|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|1D|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|1E|8|@$D|1F|E|1G|Q|R]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1H|8|@$D|1I|E|1J|Q|R]]|9|@$D|1K|E|1L|1|1M]]|A|$]]|$1|U|3|V|5|6|7|1N|8|@$D|1O|E|1P|Q|R]|$D|1Q|E|1R|Q|R]]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]|14|$5|Z|10|11|A|$12|15]]]]

I know I'm a bit late, but I hope this can help anyway.
Based on <a href="https://stackoverflow.com/users/283366/phil">Phil</a>'s answer, I created a default enumerator class that can be extended.
<pre><code>class DefaultEnum
{
 static public function getConstantText(string $constant)
 {
 try {
 // Get child class name that called this method
 $child_class = get_called_class();

 $reflection = new ReflectionClass($child_class);
 $const = $reflection-&gt;getConstant($constant);

 return $const;
 } catch (\ReflectionException $e) {
 // ...
 }
 }
}

class CustomEnum extends DefaultEnum
{
 const something = 'abcd';
 const something2 = 'ABCD';
}
</code></pre>
You can call this method like this
<pre><code>CustomEnum::getConstantText('something');
</code></pre>
It will return <code>'abcd'</code>.
The function <a href="https://www.php.net/manual/en/function.get-called-class.php" rel="nofollow noreferrer"><code>get_called_class()</code></a> is a function that returns the class name that called this method and it works specifically for static methods.
In this case <code>$child_class</code> value will be <code>CustomEnum::class</code>. ReflectionClass accepts strings and object as parameter.

I would like to be able to do something like this:

<pre><code>class ThingIDs
{
 const Something = 1;
 const AnotherThing = 2;
}

$thing = 'Something';
$id = ThingIDs::$thing;
</code></pre>

This doesn't work. Is there a straightforward way of doing something equivalent? Note that I'm stuck with the class; it's in a library I can't rewrite. I'm writing code that takes arguments on the command line, and I would really like it to take symbolic names instead of id numbers.

Get value of dynamically chosen class constant in PHP

我希望能够做这样的事情：class ThingIDs{    const Something = 1;    const AnotherThing = 2;}$thing = 'Something';$id = ThingIDs::$thing;这不管用。有没有一种简单的方法来做一些等价的事情？注意，我被这个类卡住了；它在一个我不能重写的库中。我正在编写在命令行上接受参数的代码，我真的希望它接受符

问在PHP中获取动态选择的类常量的值
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