Session errors in PHP programs

Development requires access to PHP, and it feels fast to get started. Errors always occur when debugging sessions in PHP. Warning: session_start (): Cannotsendsessioncachelimiter-headersalreadysent (outputstartedatXXX: 2) in. phponline3 is similar

Developers need to access PHP, and they feel very quick to get started. they always encounter errors when debugging sessions in PHP,

Warning: session_start (): Cannot send session cache limiter-headers already sent (output started at XXX: 2) in. php on line 3

Similar errors: the source code does not seem to have any errors.

Php start symbol

The session cannot have any character output before it starts,

The header () is the same

Advance the code and remove the leading space.

------------------- Correct

Session_start ();
$ Username;
$ Username = "test ";
Session_register ("username ");
Echo $ _ SESSION [username];
?>

------------------- Error

Session_start ();
$ Username;
$ Username = "test ";
Session_register ("username ");
Echo $ _ SESSION [username];
?>