Attach pdf from dynamic url

Question

You can try to do it in two ways.

The first one, much more simple, is to save a temporary PDF file somewhere, for example in a uploads directory, use it as attachment and delete if after the call to wp_mail() function is made:

function my_custom_save_post( $post_id, $post, $update )  {
    if( ! $update ) { return; }
    if( wp_is_post_revision( $post_id ) ) { return; }
    if( defined( 'DOING_AUTOSAVE' ) and DOING_AUTOSAVE ) { return; }
    if( $post->post_type != 'MYCUSTOMPOST' ) { return; }
    $url = wp_nonce_url( admin_url( "myCustomUrl" ), 'my_nounce_name' );
    $contents = file_get_contents( $url );
    # here temporary file name is a fixed string
    # but it better to be some unique string
    # (use current timestamp, post ID, etc)
    $tempfile = ABSPATH . 'uploads/filename.pdf';
    file_put_contents( $tempfile, $contents );
    $attachments = array( $tempfile );
    $headers="From: My Name <[email protected]>" . "\r\n";
    wp_mail( '[email protected]', 'subject', $url, $headers, $attachments );
    unlink( $tempfile );
}
add_action( 'save_post', 'my_custom_save_post', 10, 3 );

The second is just a guess and needs to be tested. WordPress rely on PHPMailer component for sending emails. That component has a addStringAttachment method which allows to attach a binary object assigned to a PHP variable as a email file attachment. Here is the question about this topic. I don’t see any way this could be used via wp_mail() function but in theory you can try to do it via phpmailer_init hook:

function my_attach_pdf( $mailer_instance ) {
    $url = wp_nonce_url( admin_url( "myCustomUrl" ), 'my_nounce_name' );
    $contents = file_get_contents( $url );
    $mailer_instance->addStringAttachment( $contents, 'your_file_name.pdf' );
}
function my_custom_save_post( $post_id, $post, $update )  {
    if( ! $update ) { return; }
    if( wp_is_post_revision( $post_id ) ) { return; }
    if( defined( 'DOING_AUTOSAVE' ) and DOING_AUTOSAVE ) { return; }
    if( $post->post_type != 'MYCUSTOMPOST' ) { return; }
    $headers="From: My Name <[email protected]>" . "\r\n";
    add_action( 'phpmailer_init', 'my_attach_pdf' );
    wp_mail( '[email protected]', 'subject', $url, $headers, $attachments );
    remove_action( 'phpmailer_init', 'my_attach_pdf' );
}
add_action( 'save_post', 'my_custom_save_post', 10, 3 );

I’m really curious if the second approach would work. Maybe give it a test one day. If you test it, please give some feedback.

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