Unexpected t_string, expecting t_variable the great gods who slept late at night, depend on you! What to do with it

Unexpected t_string, expecting t_variable the great gods who slept late at night, depend on you!
Parse error:syntax error, unexpected t_string, expecting t_variable in C:\AppServ\www\vote\db.php on line 13
Part of the code:
Class db{
private static $dbhost;
private static $dbuser;
private static $password;
private static $dbname;
private static $instance =null;

Private Function_construct ($host, $user, $pass, $db) {//line 13
Self:: $dbhost = $host;
Self:: $dbuser = $usr;
Self:: $password = $pass;
Self:: $dbname = $db;
Self::creatcon ();
}
Why is it wrong? Why? For advice

------Solution--------------------
Private Function __construct ($host, $user, $pass, $db) {

Space double underline.

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