将标题位置放置为Sql Die动作

I was curious to know if i could do this, but found no examples on line

$info_find = mysql_query("SELECT info FROM sets WHERE category = '$selected_cat'")  
or die( header ("location: index.php"));

Firstly doing it as above doesn't work. Can it be done? Are there any drawbacks?

die() just writes its parameter out, it doesn't execute it. So a "or die()" construct will not help you there.

You can consider something like

or die(createRedirect("index.php"));

with

function createRedirect($where) {
  $s='<html><head>';
  $s.='<meta http-equiv="refresh" content="1; url='.$where.'">';
  $s.='</head><body>If you are not automatically redirected click <a href="'.$where.'">here</a>';
  $s.='</body></html>';
  return $s;
}

if you are willing to accept the downsides of client-sided redirection

You can rewrite your code as

$info_find = mysql_query("SELECT info FROM sets WHERE category = '$selected_cat'")  ;
if ($info_find === FALSE) {
  header ('location: index.php');
  die();
}

But, before use the header function, be sure you haven't send any output to the browser.