PHP错误无法在写上下文中使用方法return> value

Question

I am getting this error in a PHP class...

Fatal error: Can't use method return value in write context in C:\\webserver\\htdocs\\friendproject2\\includes\\classes\\User.class.php on line 35

Here is the troubled part.

if(isset($this->session->get('user_id')) && $this->session->get('user_id') != ''){
    //run code
}

This code is in my contrustor, is a value is not already set for $this->session->get('user_id') then it will return false instead of a Number. So as you can see I was hoping to check if this value is a number or not or not even set.

Any help with fixing appreciated.

Answer 1

You can't use isset for the result of a function. Consider the following code instead:

if( $this->session->get('user_id') ){
    //run code
}

Answer 2

isset() only works with variables as passing anything else will result in a parse error. For checking if constants are set use the defined() function.

From the PHP Manual .

Answer 3

You can't use isset on a function. However, since false , 0 , and '' all equate to a falsey statement, write your test this way:

if( $id = $this->sessions->get('user_id') ){
   // Will only run if $id does not equal '', False, or 0
}

That way you have run your test and assigned the variable in one step.