【プラグインなしWordPressブログリンクカード】CSSデザインが崩れるのをカスタマイズ！

iframe {max-width:100%;}

@media only screen and (max-width : 550px) {
p.wp-embed-heading {font-size:18px;}
.wp-embed-featured-image.square {float: none; max-width: 100%; margin-right: 0;}
.wp-embed-excerpt {display:none;}
.wp-embed-footer {margin-top: 0;}
}

<?php
/*
Plugin Name: my-plugin
Plugin URI:
Description: My Plugin For WordPress.
Version: 1.0.0
Author:
Author URI:
License: GPL2
*/

if ( ! function_exists( 'nendebcom_plugin_last_load' ) ) :
/*
* my-plugin を最後に読み込むようにする。
*
* License: GPLv2 or later
*/
function nendebcom_plugin_last_load() {

$this_activeplugin  = '';
$this_plugin        = 'my-plugin/my-plugin.php';    //最後に読み込みたいプラグイン
$active_plugins     = get_option( 'active_plugins' );
$new_active_plugins = array();

foreach ( $active_plugins as $plugins ) {
if( $plugins != $this_plugin ){
$new_active_plugins[] = $plugins;
}else{
$this_activeplugin = $this_plugin;
}
}

if( $this_activeplugin ){
$new_active_plugins[] = $this_activeplugin;
}

if( ! empty( $new_active_plugins ) ){
update_option( 'active_plugins' ,  $new_active_plugins );
}
}
endif; // nendebcom_plugin_last_load
add_action( &quot;activated_plugin&quot;, &quot;nendebcom_plugin_last_load&quot; );

/*
* my-pluginの更新を非表示
*
* License: GPLv2 or later
*/
function nendebcom_hide_myplugin_updateplugin( $data ) {
if ( isset( $data-&gt;response['my-plugin/my-plugin.php'] ) ) {
unset( $data-&gt;response['my-plugin/my-plugin.php'] );
}
return $data;
}
add_filter( 'site_option__site_transient_update_plugins', 'nendebcom_hide_myplugin_updateplugin' );

/**
* embed用のCSSを my-plugin に設置したCSSの方を読込むように変更する
*
* @since WordPress 4.4.0
* License: GPLv2 or later
*/
function nendebcom_embed_styles(){
// Add wp-embed-template used in the original stylesheet.
wp_enqueue_style( 'wp-embed-template-org', plugin_dir_url( __FILE__ ) . 'wp-embed-template.css' );
}
add_filter( 'embed_head', 'nendebcom_embed_styles' );
// Remove wp-embed-template used in the main stylesheet.
remove_action( 'embed_head', 'print_embed_styles' );

/**
* アイキャッチ画像表示場所を固定
*
* Rectangular images are shown above the title
* while square images are shown next to the content.
*
* @since 4.4.0
*
* @param string $shape Thumbnail image shape. Either 'rectangular' or 'square'.
* License: GPLv2 or later
*/
add_filter( 'embed_thumbnail_image_shape', function(){ return 'square'; } );

/**
* 使用するアイキャッチ画像を設定
*
* @since 4.4.0
*
* @param string $image_size Thumbnail image size.
* License: GPLv2 or later
*/
add_filter( 'embed_thumbnail_image_size', function(){ return 'medium_large'; } );