Thinkphp 3.2.3 What is wrong with the notation of this ternary expression?

What's wrong with this notation? Session cannot be used in ternary expressions?

$data['user_id'] = isset(session('user_id')):session('user_id'):'guest';

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What's wrong with this notation? Session cannot be used in ternary expressions?

$data['user_id'] = isset(session('user_id')):session('user_id'):'guest';

Suggest you write like this

$data['user_id'] = session('user_id');if (empty($data['user_id'])) $data['user_id'] = 'guest';

Three-way proposal for

$data['user_id'] = session('user_id') ? session('user_id') : 'guest';

Isset is used to detect if a variable has been declared, rather than to check the value, otherwise a syntax error is generated.

Three-dimensional expression
condition ? p1 : p2

You're all two of them : .

Http://php.net/manual/zh/language.operators.comparison.php#language.operators.comparison.ternary

You wrote two: $data [' user_id '] = Session (' user_id ')? Session (' user_id '): ' guest ';

$data['user_id'] = isset(session('user_id'))？session('user_id'):'guest';

First of all, as stated above, judging the conditions should be? No.
Second, the Isset parameter cannot be a function return value

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