PHP：函数名中的变量
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PHP: Variable in a function name
提问by LibraryThingTim
I want to trigger a function based on a variable.
我想根据变量触发一个函数。
function sound_dog() { return 'woof'; }
function sound_cow() { return 'moo'; }
$animal = 'cow';
print sound_{$animal}(); *
The * line is the line that's not correct.
* 行是不正确的行。
I've done this before, but I can't find it. I'm aware of the potential security problems, etc.
我以前做过这个，但我找不到它。我知道潜在的安全问题等。
Anyone? Many thanks.
任何人？非常感谢。
回答by scribble
You can do that, but not without interpolating the string first:
你可以这样做，但不能不先插入字符串：
$animfunc = 'sound_' . $animal;
print $animfunc();
Or, skip the temporary variable with call_user_func():
或者，使用call_user_func()跳过临时变量：
call_user_func('sound_' . $animal);
回答by Greg Hewgill
You can do it like this:
你可以这样做：
$animal = 'cow';
$sounder = "sound_$animal";
print ${sounder}();
However, a much better way would be to use an array:
但是，更好的方法是使用数组：
$sounds = array('dog' => sound_dog, 'cow' => sound_cow);
$animal = 'cow';
print $sounds[$animal]();
One of the advantages of the array method is that when you come back to your code six months later and wonder "gee, where is this sound_cowfunction used?" you can answer that question with a simple text search instead of having to follow all the logic that creates variable function names on the fly.
数组方法的优点之一是，当您在六个月后回到您的代码并想知道“哎呀，这个sound_cow函数在哪里使用的？” 您可以通过简单的文本搜索来回答这个问题，而不必遵循动态创建变量函数名称的所有逻辑。
回答by Brendan Long
http://php.net/manual/en/functions.variable-functions.php
http://php.net/manual/en/functions.variable-functions.php
To do your example, you'd do
做你的例子，你会做
$animal_function = "sound_$animal";
$animal_function();
回答by Sam152
You should ask yourself why you need to be doing this, perhaps you need to refactor your code to something like the following:
您应该问问自己为什么需要这样做，也许您需要将代码重构为如下所示：
function animal_sound($type){
$animals=array();
$animals['dog'] = "woof";
$animals['cow'] = "moo";
return $animals[$type];
}
$animal = "cow";
print animal_sound($animal);
回答by parker_codes
You can use curly brackets to build your function name. Not sure of backwards compatibility, but at least PHP 7+ can do it.
您可以使用大括号来构建函数名称。不确定向后兼容性，但至少 PHP 7+ 可以做到。
Here is my code when using Carbon to add or subtract time based on user chosen type (of 'add' or 'sub'):
这是我使用 Carbon 根据用户选择的类型（“add”或“sub”）添加或减去时间时的代码：
$type = $this->date->calculation_type; // 'add' or 'sub'
$result = $this->contactFields[$this->date->{'base_date_field'}]
->{$type.'Years'}( $this->date->{'calculation_years'} )
->{$type.'Months'}( $this->date->{'calculation_months'} )
->{$type.'Weeks'}( $this->date->{'calculation_weeks'} )
->{$type.'Days'}( $this->date->{'calculation_days'} );
The important part here is the {$type.'someString'}sections. This will generate the function name before executing it. So in the first case if the user has chosen 'add', {$type.'Years'}becomes addYears.
这里的重要部分是{$type.'someString'}部分。这将在执行之前生成函数名称。因此，在第一种情况下，如果用户选择了“添加”，则{$type.'Years'}变为addYears。
回答by Nabi K.A.Z.
For PHP >= 7you can use this way:
因为PHP >= 7您可以使用这种方式：
function sound_dog() { return 'woof'; }
function sound_cow() { return 'moo'; }
$animal = 'cow';
print ('sound_' . $animal)();
回答by user1207013
You can use $this->and self::for class-functions. Example provided below with a function input-parameter.
您可以将$this->和self::用于类函数。下面提供了带有函数输入参数的示例。
$var = 'some_class_function';
call_user_func(array($this, $var), $inputValue);
// equivalent to: $this->some_class_function($inputValue);
