about issues and isset about page refresh recurring submissions

Source: Internet
Author: User
Questions about page Refresh repeat submission and isset



if ($_server[' request_method '] = = ' POST ') {
if (Isset ($_post[' img ')) && isset ($_post[' url '))
{
$img = $_post[' img '];
$url = $_post[' url '];
$query = sprintf (' INSERT into pic (pic,url) '.
' VALUES ('%s ', '%s ') ', $img, $url);

if (! $result = mysql_query ($query))
{
Die (' Could not insert into the database: '. mysql_error ());
}
}
}

?>




Why am I filling in an img or the URL is empty and can commit successfully, if (Isset ($_post[' img ') && isset ($_post[' url ')) This statement is wrong?


In addition, how to prevent the refresh of duplicate submissions, please God help change code!!!!

------Solution--------------------
Session_Start ();

if ($_server[' request_method '] = = ' POST ') {
if ($_post[' token ']! = $_session[' token ')
{
Die (' Token mismatch ');
}
unset ($_session[' token ');
if ($_post[' img '] && $_post[' url ')
{
$img = $_post[' img '];
$url = $_post[' url '];
$query = sprintf (' INSERT into pic (pic,url) '.
' VALUES ('%s ', '%s ') ', $img, $url);

if (! $result = mysql_query ($query))
{
Die (' Could not insert into the database: '. mysql_error ());
}
}
}
$token = MD5 (Mt_rand (0, 65535));
$_session[' token '] = $token;

?>

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