Limiting results returned from the database

Question

I want to select every photo from my database, then display them grouped by month. I have that code here:

<?php
if (isset($_COOKIE['user_id'])) {
    if (!isset($_GET['user_id'])) {
        $user_id= $_COOKIE['user_id'];
    } else {
        $user_id= $_GET['user_id'];
    }
    $connect= mysqli_connect("localhost", "root", "", "si");
    $query= "SELECT * FROM posts WHERE user_id= $user_id ORDER BY date DESC";

    $result= mysqli_query($connect, $query)
        or die('error with query');
    $date = "0";

    while ($row= mysqli_fetch_array($result)) {
        if ($date != $row['date']) {
            echo "<p> ".$row['date']."</p><br/>";
            $date = $row['date'];
        }
        echo '<img src="'.$row['picture']. '"/>' . "<br/>";
    }
}
?>

The only problem is that my code displays EVERY image from each month, this makes for an excessively large page. I want to limit my results to only 8 per month (or less if there isn't event 8 pictures for that month), then display a "show more..." link if there are more than 8. I know how to add a LIMIT to my initial query, but that won't work for this scenario. What can I do?

Here is how I want it to look:

Answer 1

add LIMIT $start, $numToDisplay

to your SQL statement, and use PHP to calculate the new values for the $start variable.

eg $pageNum = $_GET["page"] and 8 images per page means you can calculate that:

$numToDisplay = 8;
$start = ($pageNum-1)*$numToDisplay;

Answer 2

What you need to do is monitor picture count

$pickLimit = array ();
while ( $row = mysqli_fetch_array ( $result ) ) {

    if ($date != $row ['date']) {
        echo "<p> " . $row ['date'] . "</p><br/>";
        $date = $row ['date'];
    }

    $pickLimit [$date] = isset ( $pickLimit [$date] ) ? $pickLimit [$date] : 0;
    if ($pickLimit [$date] > 7)
        continue;

    echo '<img src="' . $row ['picture'] . '"/>' . "<br/>";
    $pickLimit [$date] ++;
}

Answer 3

This could be easily done using the php script whitch you already have and some css tricks, that are also used for creating an animated slider/carousel. Something like this:

<div id="carousel">
    <div id="slider">
    <?php foreach($images as $img) { ?>
        <div class="image">
            <img src="<?php echo $img; ?>" />
        </div>
    <?php } ?>
    </div>
</div>

As for the css:

#carousel {
    width: 900px; /* how much you need */
    height: 100px; /* how much you need */
    overflow: hidden;
}
#slider {
    width: auto;
    height: 100px;
}
.image {
    float: left;
}

Answer 4

This is what is known as "greatest n per group" query. If you search on here there are many examples with different solutions. Here is one of them -

SELECT *
FROM (
    SELECT
        tmp.*,
        @r := IF(@m=DATE_FORMAT(`date`, '%Y%m'), @rank + 1, 1) rank,
        @m := DATE_FORMAT(`date`, '%Y%m')
    FROM (
        SELECT *
        FROM posts
        WHERE user_id = $user_id
        ORDER BY date DESC
    ) tmp, (SELECT @m:=NULL, @r:=NULL) initvars
) tmp2
WHERE rank <= 8