Error understanding of the PHP empty () function

An error occurred yesterday in using the PHP empty () function

Can ' t use function return value in write context

The first project in the local is good, my local configuration is php5.6+apace after the project moved to the server (the server configuration is iss+php5.4) there is such a problem, after I asked a friend only to know that this is because php5.6 the following empty () Functions are not allowed to pass variables, as the parameter values in my project are scalar

So there was this problem.

Write for the first time, just record the problem and the solution.

Insights!!!

Error understanding of the PHP empty () function