我已经看到了
PHP手册.但是我不明白早期版本和更高版本的PHP之间的行为差异.我不明白这个说法：
Because this function depends on the current scope to determine parameter details,it cannot be used as a function parameter in versions prior to 5.3.0. If this value must be passed,the results should be assigned to a variable,and that variable should be passed.
