在写上下文中不能使用方法返回值

Question

The following if condition is causing an error:

if( !empty ($this -> session -> userdata( 'user_id') ) )
{
    $user_id = $this -> session -> userdata( 'user_id' );
} 
else 
{ 
    $error = "ID doesn't exist";
}

I get following error:

Fatal error: Can't use method return value in write context in (line number)

How can I fix it?

Answer 1

Replace the first if statement with if( ! $this->session->userdata('user_id') ).

The empty function check if a variable is empty but userdata is a function. Additionally, for your information, according to the CodeIgniter documentation, the userdata function returns FALSE if the item doesn't exist, which means that if user_id doesn't exist in your session, the code in the else will be executed.