Why is this function triggering on all post events? - php

Question

I've made a function that on post create, takes an URL placed in the_content and grabs an image from the URL. Then it uploads the image and attach it to the post. It works as intended. However it should only do it when the post is created, but it does it on edit and delete as well. How can I fix that?
function set_featured_image_from_content_for_galleries( $post_id ) {
$post = get_post( $post_id );
if ( 'gallery' != $post->post_type ) {
return;
}
$content = $post->post_content;
preg_match( '/https?:\/\/[^\s]+/', $content, $matches );
if ( ! empty( $matches[0] ) ) {
$image_url = $matches[0];
$image_url = preg_replace('/^(.+src=")(.+)(".+)$/', '$2', $image_url);
$upload_dir = wp_upload_dir();
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $image_url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$image_data = curl_exec($ch);
curl_close($ch);
$filename = uniqid().'.png';
if(wp_mkdir_p($upload_dir['path']))
$file = $upload_dir['path'] . '/' . $filename;
else
$file = $upload_dir['basedir'] . '/' . $filename;
file_put_contents($file, $image_data);
$wp_filetype = wp_check_filetype($filename, null );
$attachment = array(
'post_mime_type' => $wp_filetype['type'],
'post_title' => sanitize_file_name($filename),
'post_content' => '',
'post_status' => 'inherit'
);
$attach_id = wp_insert_attachment( $attachment, $file, $post_id );
require_once(ABSPATH . 'wp-admin/includes/image.php');
$attach_data = wp_generate_attachment_metadata( $attach_id, $file );
wp_update_attachment_metadata( $attach_id, $attach_data );
set_post_thumbnail( $post_id, $attach_id );
// Update post content with the new featured image URL
$image_url = wp_get_attachment_url( $attach_id );
update_post_meta( $post_id, '_post_content', $image_url);
}
}
add_action( 'save_post', 'set_featured_image_from_content_for_galleries' );
Tried to use update_post_meta() instead of the newer tag

Answer 1

You could try using the transition_post_status hook instead, which checks whether the post has changed from one status to another.
So your action would be something like:
add_action( 'transition_post_status', 'set_featured_image_from_content_for_galleries', 10, 3 );
Noting that the hook needs three parameters: $new_status, $old_status, $post, where $post is the post object. So you'd need to update your function declaration as well to:
function set_featured_image_from_content_for_galleries( $new_status, $old_status, $post ) {
And then remove $post = get_post( $post_id ); from the function, since the entire post object is already being passed.
From there you could add a check to your function to determine whether the post has already been published by checking whether it's moving to publish from the auto-draft status that WordPress uses when it initially auto-saves the post:
if ( 'publish' === $new_status && 'auto-draft' === $old_status ) {
// Do stuff...
}
You might have to play around with the logic but it seems like it should work.