The parameters of the empty function can only be variables before the PHP5.5 version

PHP5.5 and the previous version of the empty function, the development needs to note that if your local development PHP version is more than PHP5.5, and the server is less than PHP5.5, pay more attention to this problem, the need for friends can refer to the next

Before the PHP5.5 version, empty parameters cannot be complex types such as functions, only variables.

Summarize the use scenario of the empty function:

Prior to 1.PHP 5.5, this function was used to check whether a variable was assigned a value of 0, False, an empty string, or null. Any argument in the form of a non-variable causes the function to error.
2.PHP 5.5 This function can be applied to any value, not limited to a variable. Can be constants, return values for functions, and so on.

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