Question

Code:

<?php 
if (isset($_REQUEST['g'])) {
    if ($_REQUEST['g'] == "Set") {
        $g = strtolower($_REQUEST['g'])."_title";
    }else{
        $g = strtolower($_REQUEST['g']);
    }
    $result1 = mysql_query("SELECT LEFT($g, 1) FROM cards GROUP BY $g ORDER BY $g ASC");
    while ($row = mysql_fetch_array($result1)) { 
?> 
<a href="./index.php?route=<?php echo $var[0]."/".$var[1]."&g=".$_REQUEST['g']; ?>&sort=<?php echo substr($row[$g], 0, 1); ?>"><?php echo substr($row[$g], 0, 1); ?></a>&nbsp;     
<?php 
    } 
}
?>

Error Message:

Notice: Undefined index: set_title in E:\xampp\htdocs\zipdown\include\sort.php on line 11

What am i missing?

Answer 1

Don’t forget to escape the value of $g if it isn’t known to be Set.

$g = mysql_real_escape_string($g);

Alias the column created by LEFT() as $g, enclosed in backticks:

$result1 = mysql_query("SELECT LEFT(`$g`, 1) AS `$g` FROM cards GROUP BY `$g` ORDER BY `$g` ASC");
//----------------------------------------^^^^^^^

Otherwise, the column name returned by your mysql_fetch_array() call is something like:

$row['LEFT(set_title,1)']

Note on security:

Given that your database must have a finite set of column names, it is advisable to use a whitelist against which you check the value of $g:

// Assuming your columns are named title, author, etc...
if (in_array($g, array('title','author','set_title','publisher','whatever'))) {
   // do the rest of your work
}
else {
   // Invalid value to $_REQUEST['g']
}