Php Note: empty () only checks variables as anything Error

Today, when we use the empty () function to determine whether a variable is null, the following message is displayed: empty () only checks variables as anything else will result in a parse error. in other words, the following will not work: empty (trim ($ name )). an error occurred. I found the problem all day later.

When you use empty to check the results returned by a function, the following fatal error is reported:

Fatal error: Can't use function return value in write context in :..................

For example:

Echo empty (yourfunction (xx, oo ));

Go to the PHP manual and check the following text in the description of the empty function:

Note: empty () only checks variables as anything else will result in a parse error. In other words, the following will not work: empty (trim ($ name )).

Empty () only detects variables, and any non-variables will cause parsing errors!

Therefore, we cannot use empty to directly detect the value returned by the function. We need to first assign the return value of the function to a variable, and then use empty to detect the variable.

Therefore, we can write it as follows:

$ Return = yourfunction (xx, oo );

Echo empty (return );