Will someone handle this exception?

Will someone make such an error? Error message: Warning: & nbsp; session_start () & nbsp; [function. session-start]: & nbsp; Cannot & nbsp; send & nbsp; session & nbsp; cookie & nbsp;-& nbsp; headers & nbsp; will someone make a mistake like?
The error message is:
Warning: session_start () [function. session-start]: Cannot send session cookie-headers already sent by (output started at/www/web/jiayiblog_com/public_html/buy. php: 2) in/www/web/jiayiblog_com/public_html/buy. php on line 2

Warning: session_start () [function. session-start]: Cannot send session cache limiter-headers already sent (output started at/www/web/jiayiblog_com/public_html/buy. php: 2) in/www/web/jiayiblog_com/public_html/buy. php on line 2

Warning: Cannot modify header information-headers already sent by (output started at/www/web/jiayiblog_com/public_html/buy. php: 2) in/www/web/jiayiblog_com/public_html/buy. php on line 58
The error is like this, and the code of buy. php is:


Ob_start ();
$ Parray = $ _ SESSION ["mycar"];
?>




Include_once ("functions/databaseconnection. php ");
$ Arr = array ();
$ Name = $ _ GET ["name"];
$ Con = "select * from allproduct where name = '$ name '";
GetConnection ();
$ Result = mysql_query ($ con );
While ($ result1 = mysql_fetch_array ($ result )){
$ Arr [] = $ result1;

}
$ Pname = $ arr [0] ['name'];
$ Pprice = $ arr [0] ['price'];
$ Pfare = $ arr [0] ['fare'];
$ Id = $ arr [0] ['id'];

If ($ id = ""){
If (! Is_array ($ parray )){
Echo ("your shopping cart has no items ");
}
Else {
Header ("location: car. php ");
}


}
Else {
If (is_array ($ parray )){
If (array_key_exists ($ id, $ parray )){
$ Uu = $ parray [$ id];
$ Uu ["num"] = $ uu ["num"] + 1;
$ Parray [$ id] = $ uu;

}
Else {
$ Parray [$ id] = array ("id" => $ id, "name" => $ pname, "price" => $ pprice, "fare" => $ pfare, "num" => 1 );

}

}

Else {

$ Parray [$ id] = array ("id" => $ id, "name" => $ pname, "price" => $ pprice, "fare" => $ pfare, "num" => 1 );
}

$ _ SESSION ["mycar"] = $ parray;
Ob_clean ();
Header ("location: car. php ");

}



?>
Why? Could you please help me? is it the question of session_start? You are in trouble.
------ Solution --------------------
The session must be at the beginning
------ Solution --------------------
Put session_start to the first line.
------ Solution --------------------

  This problem occurs: session_start (); must be before output.
Changed to this:
Session_start ();
?>

------ Solution --------------------
Session_start ();
No output before
Header is also
The BOM in UTF8 format does not work either.
------ Solution --------------------
Before the first line of the program
Ob_start ();