How do I get attachment_id?

Question

This is trivial, but I can't really find an answer, I've seen some hints like search in database etc., but this is madness.

Basically, I have a metabox with upload button that allows you to upload or pick existing image from Media Library, that's how I get the URL of this image:

$my_image = get_post_meta($post->ID, '_my_image_metabox', true);

Of course I do want exact size of this image to be displayed so I need to use:

wp_get_attachment_image_src($attachment_id, 'desired-size');

The question is how do I get attachment_id of _my_image_metabox? I've been searching literally everywhere and there are no sane answers, how is wp_get_attachment_image_src() supposed to work if there's not a single line on getting $attachment_id in Codex whatsoever? :)

[updated]

var_dump($my_image) returns:

array(1) { [0]=> string(86) "http://localhost/theme/wp-content/uploads/2014/10/my_image.jpg" }

Saving the data is pretty complicated as I use my own metabox generating class, something like this: https://github.com/nyordanov/SmartMetaBox/blob/master/SmartMetaBox.php

How do I inject the proper attachment_id to my_image then? I'd add I have multiple (10) fields like this one and would like every single one to have separate, unique attachment_id.

Answer 1

Ok, all those hipercomplex functions can be reduced to one simple command: attachment_url_to_postid

You only need to parse the image url to retrieve the attachment id:

<?php

   $attachment_id = attachment_url_to_postid( $image_url );
   echo $attachment_id;

?>

That's all you need.

Answer 2

I am too late to answer this question but it will worked.

$attachment_id = get_post_thumbnail_id( $post->ID );
$url = wp_get_attachment_image_src($attachment_id, 'desired-size');

Answer 3

I had the same problem while I was using CMB plugin, I solved adding a custom function to functions.php to get the image ID using the image url:

functions.php

function cmb_get_image_id($image_src) {
    global $wpdb;
    $image = $wpdb->get_col($wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE guid='%s';", $image_src )); 
    return $image[0]; //return the image ID
}

In your theme:

$my_image = get_post_meta($post->ID, '_my_image_metabox', false);
$attachment_id = cmb_get_image_id($my_image);
wp_get_attachment_image_src($attachment_id, 'desired-size');

Answer 4

What I do in such cases in that save the id in a hidden input along with the URL.

function meta_image_upload() {
    global $post;
    $my_image = get_post_meta($post->ID, '_my_image_metabox', true);
    $my_image_id = get_post_meta($post->ID, '_my_image_id_metabox', true);

    $out = '<input id="my_image" type="text" name="my_uploaded_image" value="'. $my_image .'">';
    $out .= '<input id="my_image_id" type="hidden" name="my_uploaded_image_id" value="'. $my_image_id .'">';
    $out .= '<button id="my_image_upload">Upload Image</button>';

    echo $out;
}  

On the upload handler script:

attachment = custom_uploader.state().get('selection').first().toJSON();
    $('#my_image').val(attachment.url);
    $('#my_image_id').val(attachment.id); // Just add this line

Then at other callbacks :

global $post;
$my_image_id = get_post_meta($post->ID, '_my_image_id_metabox', true);
wp_get_attachment_image_src($my_image_id, 'desired-size');

That's just my solution and someone might come up with a better one. However, I found it faster than querying database to fetch the associated attachment id.

Answer 5

All the post meta you're saving is being attached to a post of type attachment, so You can consider $post->ID is the attachment ID.

Answer 6

Try with this:

$attachment_id = $wpdb->get_var( 
    $wpdb->prepare( 
        "SELECT wposts.ID 
            FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta 
            WHERE wposts.ID = wpostmeta.post_id 
            AND wpostmeta.meta_key = '_wp_attached_file' 
            AND wpostmeta.meta_value = '%s' 
            AND wposts.post_type = 'attachment'", 
        $url
    ) 
);