[WP]アイキャッチの設定とデフォルト画像の登録

default_eyecatch.php

<?php

// アイキャッチの設定とデフォルト画像の登録
add_action('init', function() {
    add_theme_support('post-thumbnails');

    $filename = dirname(__FILE__) . "/img/no_image.png";
    if (file_exists($filename)) {
        $wp_upload_dir = wp_upload_dir();
        $upload_path = $wp_upload_dir['path'];
        $new_path = $upload_path . "/no_image.png";
        rename($filename, $new_path);
        $filetype = wp_check_filetype( basename( $new_path ), null );
        $attachment = array(
            'guid'           => $wp_upload_dir['url'] . '/' . basename( $new_path ),
            'post_mime_type' => $filetype['type'],
            'post_title'     => preg_replace( '/\.[^.]+$/', '', basename( $new_path ) ),
            'post_content'   => '',
            'post_status'    => 'inherit'
        );
        $attach_id = wp_insert_attachment( $attachment, $new_path);
        require_once( ABSPATH . 'wp-admin/includes/image.php' );
        $attach_data = wp_generate_attachment_metadata( $attach_id, $new_path );
        wp_update_attachment_metadata( $attach_id, $attach_data );
    }
});

attach_idを一意にしたい