Basic related questions, beginner, thank you very much

Basic problem, rookie help, thank you very much.
$u 1_nick = $this->session->userdata (' userinfo ') [' screen_name '];

If the code above, in NetBeans error, error is:
"Syntax error:
Expected: instanceof, as,->, =>,}, ', ', OR, XOR, and, =, + =,-=, *=,/=,. =,%=, &=, |+, ^=, <<=, >>=,? , '; ', | |, &&, |, ^, &, = =,! =, = =,!==, <=+, >=+, <, <<, +,-, *,/,%, '. ', ++, --, ], ), ':'
"
I am pure PHP novice, please guide me, why in other people there is no problem, is not I have some PHP features not open? Thank you very much.

------Solution--------------------
What is the complete error message? Var_dump ($this->session->userdata (' userinfo ')); Post the results
------Solution--------------------
$u 1_nick = $this->session->userdata (' userinfo ') [' screen_name '];
This usage is only legal in php5.4.

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