SNSに投稿を共有するためのOGP（Open Graph Protocol）を設定。
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width">
<?php if( is_single() ): ?>
<meta property="og:site_name" content="<?php bloginfo( 'name' ) ?>">
<meta property="og:locale" content="ja_JP">
<meta property="og:type" content="article">
<meta property="og:title" content="<?php the_title(); ?>">
<meta property="og:url" content="<?php the_permalink(); ?>">
<meta property="og:description" content="<?php echo esc_attr( wp_strip_all_tags( get_the_excerpt() ) ); ?>">
<?php if( has_post_thumbnail() ): ?>
<?php $site_img = get_post_thumbnail_id(); ?>
<meta property="og:image" content="<?php echo esc_url( wp_get_attachment_url( $site_img ) ); ?>">
<meta property="og:image:width" content="<?php echo esc_url( wp_get_attachment_metadata( $site_img )['width'] ); ?>">
<meta property="og:image:height" content="<?php echo esc_url( wp_get_attachment_metadata( $site_img )['height'] ); ?>">
<?php endif; ?>
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:site" content="TwitterのアカウントID（@を含めて）">
<?php endif; ?>
<?php wp_head(); ?>
</head>
