三元运算符 - 我做错了什么？

Question

$profilePic = isset( $userservice->getProfilePic($userid))      
              ?  filter($userservice->getProfilePic($userid)) 
              : '<img></img>';

Returns the error:

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

What am I doing wrong here?

Answer 1

You can only use isset with variables, not with return values from functions, as isset is not a function, but a language construct.

addendum : There was a vote to allow passing arbitrary expression arguments to isset and empty , but finally isset was dropped from the final implementation.

Answer 2

isset only and exclusively works on variables. You do not need it for functions. Your ternary operator is fine.

See The Definitive Guide To PHP's isset And empty .

Answer 3

try: "

$tempPic=$userservice->getProfilePic($userid);
         $profilePic = isset($tempPic ) ?  filter($userservicegetProfilePic($userid))  : '<img></img>';

"