就像我们取消设置变量一样，如何取消设置函数定义?
问题描述：
我想定义一个函数并在使用后取消设置它，就像处理变量一样.
I want to define a function and unset it after its use just like we do with variables.
$a = 'something';
unset($a);
echo $a; // outputs nothing
就像这样，如果我声明一个函数 callMethod()，是否可以取消设置它?
Just like this if i declare a function callMethod(), is there a way to unset it?
答
从PHP 5.3开始，您可以分配将匿名函数设置为变量，然后将其取消设置:
As of PHP 5.3, you can assign an anonymous function to a variable, then unset it:
$upper = function($str) {
return strtoupper($str);
};
echo $upper('test1');
// outputs: TEST1
unset($upper);
echo $upper('test2');
// Notice: Undefined variable: upper
// Fatal error: Function name must be a string
在5.3之前，您可以使用 create_function() 做类似的事情
Before 5.3, you can do something similar with create_function()
$func = create_function('$arg', 'return strtoupper($arg);');
echo $func('test1');
unset($func);
$func2 = "\0lambda_1";
echo $func2('test2.a'), "\n"; // Same results, this is the "unset" $func function
echo $func('test2.b'); // Fatal Error