Multiple Images/ Slider with custom post [single.php] - wordpress

Question

I am looking for a approach to add multiple images option under the Feature image section in wordPress custom post type. I will integrate/implement these images on single.php file where I want to show the slider images. I want to do it using Codex / coding approach, Please NO PLUGIN. Any Idea/help will be appreciated.
EDIT
I have found this code and it has to be pasted in function.php or plugin.php. I have create a new file plug-slider.php and add the below code there & its not working, but the issue is that I have to call each image separately instead like create an array and call the array, also if there is no second/third image set for other post then the slider block is showing empty.. I don't know why, may be I am missing something... can someone please review.
Code Reference: Stack overflow question
//init the meta box
add_action( 'after_setup_theme', 'custom_postimage_setup' );
function custom_postimage_setup(){
add_action( 'add_meta_boxes', 'custom_postimage_meta_box' );
add_action( 'save_post', 'custom_postimage_meta_box_save' );
}
function custom_postimage_meta_box(){
//on which post types should the box appear?
$post_types = array('portfolios','page');
foreach($post_types as $pt){
add_meta_box('custom_postimage_meta_box',__( 'More Featured Images', 'yourdomain'),'custom_postimage_meta_box_func',$pt,'side','low');
}
}
function custom_postimage_meta_box_func($post){
//an array with all the images (ba meta key). The same array has to be in custom_postimage_meta_box_save($post_id) as well.
$meta_keys = array('second_featured_image','third_featured_image');
foreach($meta_keys as $meta_key){
$image_meta_val=get_post_meta( $post->ID, $meta_key, true);
?>
<div class="custom_postimage_wrapper" id="<?php echo $meta_key; ?>_wrapper" style="margin-bottom:20px;">
<img src="<?php echo ($image_meta_val!=''?wp_get_attachment_image_src( $image_meta_val)[0]:''); ?>" style="width:100%;display: <?php echo ($image_meta_val!=''?'block':'none'); ?>" alt="">
<a class="addimage button" onclick="custom_postimage_add_image('<?php echo $meta_key; ?>');"><?php _e('add image','yourdomain'); ?></a><br>
<a class="removeimage" style="color:#a00;cursor:pointer;display: <?php echo ($image_meta_val!=''?'block':'none'); ?>" onclick="custom_postimage_remove_image('<?php echo $meta_key; ?>');"><?php _e('remove image','yourdomain'); ?></a>
<input type="hidden" name="<?php echo $meta_key; ?>" id="<?php echo $meta_key; ?>" value="<?php echo $image_meta_val; ?>" />
</div>
<?php } ?>
<script>
function custom_postimage_add_image(key){
var $wrapper = jQuery('#'+key+'_wrapper');
custom_postimage_uploader = wp.media.frames.file_frame = wp.media({
title: '<?php _e('select image','yourdomain'); ?>',
button: {
text: '<?php _e('select image','yourdomain'); ?>'
},
multiple: false
});
custom_postimage_uploader.on('select', function() {
var attachment = custom_postimage_uploader.state().get('selection').first().toJSON();
var img_url = attachment['url'];
var img_id = attachment['id'];
$wrapper.find('input#'+key).val(img_id);
$wrapper.find('img').attr('src',img_url);
$wrapper.find('img').show();
$wrapper.find('a.removeimage').show();
});
custom_postimage_uploader.on('open', function(){
var selection = custom_postimage_uploader.state().get('selection');
var selected = $wrapper.find('input#'+key).val();
if(selected){
selection.add(wp.media.attachment(selected));
}
});
custom_postimage_uploader.open();
return false;
}
function custom_postimage_remove_image(key){
var $wrapper = jQuery('#'+key+'_wrapper');
$wrapper.find('input#'+key).val('');
$wrapper.find('img').hide();
$wrapper.find('a.removeimage').hide();
return false;
}
</script>
<?php
wp_nonce_field( 'custom_postimage_meta_box', 'custom_postimage_meta_box_nonce' );
}
function custom_postimage_meta_box_save($post_id){
if ( ! current_user_can( 'edit_posts', $post_id ) ){ return 'not permitted'; }
if (isset( $_POST['custom_postimage_meta_box_nonce'] ) && wp_verify_nonce($_POST['custom_postimage_meta_box_nonce'],'custom_postimage_meta_box' )){
//same array as in custom_postimage_meta_box_func($post)
$meta_keys = array('second_featured_image','third_featured_image');
foreach($meta_keys as $meta_key){
if(isset($_POST[$meta_key]) && intval($_POST[$meta_key])!=''){
update_post_meta( $post_id, $meta_key, intval($_POST[$meta_key]));
}else{
update_post_meta( $post_id, $meta_key, '');
}
}
}
}
My Callback code in single.php
<div class="project-carousel owl-carousel js-project-carousel">
<?php
while(have_posts()) {
the_post(); ?>
<!-- <div class="project-detail-item">
<?php //the_post_thumbnail('portfolio-slider') ?>
</div> -->
<?php
$slider_img=wp_get_attachment_image(get_post_meta(get_the_ID(),'second_featured_image', true),'full');
if($slider_img !='')
{?>
<div class="project-detail-item">
<?php
echo wp_get_attachment_image(get_post_meta(get_the_ID(),'second_featured_image', true),'full');
?>
</div>
<?php }
else
{
the_post_thumbnail('portfolio-slider');
}
?>
</div>
again the if/else block works for the empty check but only for single instance, like I have to check for each image... or I messed up?

Answer 1

Please do the below change and then try...
in your plugin file change this line.
$meta_keys = array('second_featured_image','third_featured_image');
To
$meta_keys = array('second_featured_image','third_featured_image','fourth_featured_image','fifth_featured_image');
change your call back single.php file code to something like below. Loop through each file and check for empty.
I have modified the code to accept up to 5/6 images so you can use it in the slider.
<div class="project-carousel owl-carousel js-project-carousel">
<?php
while(have_posts()) {
the_post();
$slider_img=the_post_thumbnail('portfolio-slider');
$slider_img1=wp_get_attachment_image(get_post_meta(get_the_ID(),'second_featured_image', true),'full');
$slider_img2=wp_get_attachment_image(get_post_meta(get_the_ID(),'third_featured_image', true),'full');
$slider_img3=wp_get_attachment_image(get_post_meta(get_the_ID(),'fourth_featured_image', true),'full');
$slider_img4=wp_get_attachment_image(get_post_meta(get_the_ID(),'fifth_featured_image', true),'full');
$slider_img5=wp_get_attachment_image(get_post_meta(get_the_ID(),'six_featured_image', true),'full');
$slider_img6=wp_get_attachment_image(get_post_meta(get_the_ID(),'svn_featured_image', true),'full');
if($slider_img !='')
{?>
<div class="project-detail-item">
<?php echo $slider_img;?>
</div>
<?php }?>
<?php if($slider_img1 !=''){ ?>
<div class="project-detail-item">
<?php echo $slider_img1; ?>
</div>
<?php }?>
<?php if($slider_img2 !=''){ ?>
<div class="project-detail-item">
<?php echo $slider_img2; ?>
</div>
<?php }?>
<!--image-->
<?php if($slider_img3 !=''){ ?>
<div class="project-detail-item">
<?php echo $slider_img3; ?>
</div>
<?php }?>
<!--image end-->
<!--image-->
<?php if($slider_img4 !=''){ ?>
<div class="project-detail-item">
<?php echo $slider_img4; ?>
</div>
<?php }?>
<!--image end-->
<!--image-->
<?php if($slider_img5 !=''){ ?>
<div class="project-detail-item">
<?php echo $slider_img5; ?>
</div>
<?php }?>
<!--image end-->
<!--image-->
<?php if($slider_img6 !=''){ ?>
<div class="project-detail-item">
<?php echo $slider_img6; ?>
</div>
<?php }?>
<!--image end-->
</div>