Question

I’m trying out my first recursive function (at least I think I am!) and it only half works. First, the code:

function check_title($i,$title) {
    $q=mysql_query("SELECT Title FROM posts WHERE Title = '$title'");
    $num=mysql_num_rows($q);
    if($num==0) {
            return $title;
    }else {
            $title=$title.' ('.$i++.')';
            check_title($i,$title);
    }
}

What I’m doing is taking a string (title) and checking if that title exists in the db already. If it does, I want to append a number to the newer of the duplicates (e.g. ‘I Am A Title’ becomes ‘I Am A Title-2’). I then need to run the function again to check this new version of my title, and increase the appended value as required (‘I Am A Title-3’). Once no duplication is discovered, return the Title in its acceptable form.

It works when no duplication is found (the easy bit), but fails when duplication is found. Instead of appending a number, the entire title variable is emptied.

Any help would by greatly appreciated!

Answer 1

Use a loop instead…

$record_exists = true;
$title_base = "I Am A Title";
$title = $title_base;
$i = 0;
while($record_exists) {
    $q=mysql_query("SELECT Title FROM posts WHERE Title = '$title'");
    $num=mysql_num_rows($q);
    if($num==0) {
        $record_exists = false;
        // Exit the loop.
    }
    else {
        $i++;
        $title = $title_base . "-" . $i;
    }
}

echo $title; // last existing title

However, optimally you’d do more work with a single SQL query and iterate the result, saving a lot of trips to and from the database.

And just for fun…

$title_base = "I Am A Title";
$title = $title_base;
for ($i=1, $num=1; $num != 0; $i++)
{
    $q=mysql_query("SELECT Title FROM posts WHERE Title = '$title'");
    $num=mysql_num_rows($q);
    $title = $title_base . "-" . $i;
}

echo $title; // next title in sequence (doesn't yet exist in the db)