为幻灯片显示实现下一个和后一个按钮

Question

I'm trying to make a php slideshow and I'm almost done I just need to implement the next and back buttons which I thought were going to be easy, but apparently you can't increment indexes in php?

$sql = "SELECT pic_url FROM pic_info";
$result = $conn->query($sql);
$count = 0;
$dir = "http://dev2.matrix.msu.edu/~matrix.training/Holmberg_Dane/";
$source = "gallery.php";

if ($result->num_rows > 0) {
// output data of each row
    $pic_array = array();
    while ($row = $result->fetch_assoc()) {

        $pic_array[$count] = $row['pic_url'];
        $count++;
    }

    $index = 1;
    echo "<img src= ' $dir$pic_array[$index]' />";

    echo "<a href= '$dir$pic_array[$index + 1]'>next</a>";
    echo "<a href= '$dir$pic_array[$index - 1]'>back</a>";
}



$conn->close();

?>

Answer 1

Try this

<?php
echo '<img src="'.$dir.$pic_array[$index].'">
<a href="'.$dir.$pic_array[($index + 1)].'">next</a>
<a href="'.$dir.$pic_array[($index - 1)].'">back</a>';
?>