How to avoid to display duplicates from random images script?

Question

the following script is perfect for my needs but unfortunately displays very often duplicate images.

How can I modify to fix this issue?

Or in place of this is there a similar script allowing to display random images in one column and each of them its own link?

Thanks.

<?php

function display_random_img($array) {
$key = rand(0 , count($array) -1);
$link_url = $array[$key]['url'];
$alt_tag = $array[$key]['alt'];
$random_img_url = $array[$key]['img_url'];
list($img_width, $img_height) = getimagesize($random_img_url);
return "<a href=\"$link_url\"><img src=\"$random_img_url\" width=\"$img_width\" height=\"$img_height\" alt=\"$alt_tag\" /></a>";
}
//-----------------------
$ads_array = array(
array(
    'url' => 'http://www.mysite.com/',
    'alt' => 'Image1',
    'img_url' => 'http://www.mysite.com/pic1.jpg'
),
array(
    'url' => 'http://www.yoursite.com/',
    'alt' => 'Image2',
    'img_url' => 'http://www.mysite.com/pic2.jpg'
),
array(
    'url' => 'http://www.theirsite.com/',
    'alt' => 'Image3',
    'img_url' => 'http://www.mysite.com/pic3.jpg'
)
);
//-----------------------
$ads_array_1 = array( 
array(
    'url' => 'http://www.mysite.com/',
    'alt' => 'Image1',
    'img_url' => 'http://www.mysite.com/pic1.jpg'
),
array(
    'url' => 'http://www.yoursite.com/',
    'alt' => 'Image2',
    'img_url' => 'http://www.mysite.com/pic2.jpg'
),
array(
    'url' => 'http://www.theirsite.com/',
    'alt' => 'Image3',
    'img_url' => 'http://www.mysite.com/pic3.jpg'
)
);

//-----------------------
$ads_array_2 = array( 
array(
    'url' => 'http://www.mysite.com/',
    'alt' => 'Image1',
    'img_url' => 'http://www.mysite.com/pic1.jpg'
),
array(
    'url' => 'http://www.yoursite.com/',
    'alt' => 'Image2',
    'img_url' => 'http://www.mysite.com/pic2.jpg'
),
array(
    'url' => 'http://www.theirsite.com/',
    'alt' => 'Image3',
    'img_url' => 'http://www.mysite.com/pic3.jpg'
)
);

//-----------------------
echo display_random_img($ads_array);
echo display_random_img($ads_array_1); 
echo display_random_img($ads_array_2);
?>

hek2mgl · Accepted Answer · 2013-04-21 16:10:17Z

1

If you have just 3 images in your set of images it is a chance of 1/3 that the image is displayed two times. So increase your list of images.

However, you should use mt_rand() what will give you better randomness. But the main problem is the small amount of images

Update:

After thinking a little bit about your question, I think you need something like this:

You'll need just one array:

$ads_array = array(
array(
    'url' => 'http://www.mysite.com/',
    'alt' => 'Image1',
    'img_url' => 'http://www.mysite.com/pic1.jpg'
),
array(
    'url' => 'http://www.yoursite.com/',
    'alt' => 'Image2',
    'img_url' => 'http://www.mysite.com/pic2.jpg'
),
array(
    'url' => 'http://www.theirsite.com/',
    'alt' => 'Image3',
    'img_url' => 'http://www.mysite.com/pic3.jpg'
)
);

And this function which uses shuffle() to generate randomness:

function display_random_images($array, $maxcount = 3) {
    // shuffle $array elements
    shuffle($array);
    $html = '';
    for($i = 0; $i < min(count($array), $maxcount); $i++) {
        $img = $array[$i];
        $link_url = $img['url'];
        $alt_tag = $img['alt'];
        $random_img_url = $img['img_url'];
        list($img_width, $img_height) = getimagesize($random_img_url);
        $html .= "<a href=\"$link_url\"><img src=\"$random_img_url\" width=\"$img_width\" height=\"$img_height\" alt=\"$alt_tag\" /></a>";
    }
    return $html;
}

Now call the function, it will output $maxcount images, which are per default 3

echo display_random_images($ads_array);

If you have more images, then you can call it like this:

echo display_random_images($ads_array, 10); // 10 imgs or whatever

edited Apr 21, 2013 at 16:10

answered Apr 20, 2013 at 0:36

hek2mgl

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3 Comments

mattew Over a year ago

Thanks for your answer, but as i want to use this script for ad banners on my site, i can't add more images.

mattew Over a year ago

I tried your suggestion but it doesn't work. No picture displayed. I didn't find where is the issue :( Did you test it? It happens only to me? Thanks

hek2mgl Over a year ago

There was a little typo. I've used once $maxount instead of $maxcount. Fixed this. Can you try again?

Virus721 · Accepted Answer · 2013-04-20 00:49:01Z

0

This might work, or at least that' the idea :

function display_random_img($array) {
    static $displayedImages = array();
    // ...
    $length = count($array);
    if(count($displayedImages) === $length) {
        // Every image was picked, restarting.
        $displayedImages = array();
    }
    while(true) {
        $rand = rand(0, $length - 1);
        if( ! isset($array[$rand])) {
            // Image at $rand not shown yet.
            $displayImages[$rand] = true;
            break;
        }
    }
    $imageDetails = $array[$rand];
    // ...
}

Could be slow with huge image arrays though

answered Apr 20, 2013 at 0:49

Virus721

8,41314 gold badges78 silver badges130 bronze badges

2 Comments

mattew Over a year ago

It doesn't work :( This is the message that the system displays: "PHP cpu time limit exceeded in display_random_img()..."

Virus721 Over a year ago

I'm just giving you the idea, it's up to you to find eventual mistakes.

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