Random display of banners using php?

[thulaseeram]

Hi to All,

Here i have the same image stored in the db with different id's and also exist some other images.

Here i have to display banner randomly i have taken imageid's and displayed randomly. Because of same image stored many time i have to wait long time(refresh the page) for change of image.

Here the issue is though if i have same image stored in the db many times i have to display unique image on every refresh of the page.( means previously displayed image should not display if i refresh the page instead fresh image should appear.)

please help me some one in solving this

Thanks in Advance

Ram

[coolsti]

I really do not understand what you mean with all the images stored in the database talk.

But let us say you have a series of images, and you wish one of them to appear in the banner when a user requests a page, and which one does appear is to be random.

Then all you have to do is name the images such that there is an integral counter in the name, for example let us say you have 5 images, so name them something like bimg1.jpg, bimg2.jpg, bimg3.jpg, bimg4.jpg, bimg5.jpg.

Then when the user makes a page request and calls your PHP script, you generate a random integer, here in this example limited between the values 1 and 5, and then you build up the name of the image using this value, e.g.

$imagename = 'bimg' . $randomnumber . '.jpg';
 

and you build up the HTML that you send out to the user with the banner image pointing at this image.

You adjust this idea if your images are in a database rather than just available on the server as image files, but the idea should be the same.

[ronverdonk]

I sure hope coolsti got it right, because I have no clue what your problem or question is! If you want more support on this, please explain your problem or question in plain and clear english.

Ronald

[Atli]

Sounds to me like your trying to display a random image, but you don't want the same image to appear twice in a row?

If so you can simply store the image of the last image you display in the $_SESSION and have your random generator re-generate an ID if that ID comes up.

Something like:

<?php
// Get the last number used
//  @ silences the warning displayed if the session is empty
$last = @$_SESSION['lastNumber'];
 
// Generate random number that is not the same as the last number
do {
  $next = mt_rand(0, 10);
} while ($next == $last);
 
// Add the new number to the session and show an image.
$_SESSION['lastNumber'] = $next;
echo "<img src='image_nr_{$next}.jpg' />";
?>
 

[Markus]

I think he's saying the same image is uploaded many times but with a different name. Therefore, the image is displayed multiple times because one cannot differentiate between the images.

Unfortunately i can see no way of comparing images - may be a phpgd trick?

[Atli]

I think he's saying the same image is uploaded many times but with a different name. Therefore, the image is displayed multiple times because one cannot differentiate between the images.

Unfortunately i can see no way of comparing images - may be a phpgd trick?

Why would an image get uploaded multiple times?

But if that is the case, a quick and dirty way to identify them would be to compare file sizes and dimensions, but that would most definitely return false positives every so often.

It would even be possible to sample the data from within the image at set intervals to see if they match.

[TheServant]

It would even be possible to sample the data from within the image at set intervals to see if they match.

Or doing that if it returns the same size/dimensions. But I am unsure how you could do that.

[Atli]

Or doing that if it returns the same size/dimensions. But I am unsure how you could do that.

You could use the Filesystem functions.

Somewhat like this:

function files_compare($file1, $file2, $numSamples=10) 
{
    // Check file size
    if(filesize($file1) != filesize($file2)) {
        return false;
    }
 
    // Open streams
    $fha = fopen($file1, "r");
    $fhb = fopen($file2, "r");
 
    // Calculate offset
    $offset = (filesize($file1) / ($numSamples + 1));
 
    // Get and check samples
    for($i = 0; $i < $numSamples; $i++) {
        // Seek forward
        fseek($fha, $offset, SEEK_CUR);
        fseek($fhb, $offset, SEEK_CUR);
 
        // Take samples
        if(fread($fha, 16) != fread($fhb, 16)) {
            return false;
        }
    }
 
    // Close streams
    fclose($fha);
    fclose($fhb);
 
    // All tests passed
    return true;
}
 

[TheServant]

Very nice! Just wondering, what does offset mean in that code?

[Atli]

Very nice! Just wondering, what does offset mean in that code?

It's the amount of bytes between the samples.
In a 1000byte file, using 10 samples, it would jump 90 bytes forward into the files before taking each sample.