Tenderfeel/CustomDie.php

## CustomDie.php
<?php
/**
 * 味気ないwp_dieの出力を変更する
 */
class CustomDie {

  public function __cosntruct() {
  }

  public function enable_custom_die() {
    add_filter( 'wp_die_handler', array($this, 'die_handler') );
  }

  public function die_handler($function){
    if(!is_admin()) {
      return array($this, 'die');
    }
  }

  /**
   * Get maintenance mode page css
   *
   * @since 1.0
   * @return string
   */
  private function get_stylesheet() {
    $filename = apply_filters('maintenance_css_filename', '/css/maintenance.css');

    if (!validate_file($filename)) {
      $url = apply_filters('maintenance_css_url', get_stylesheet_directory() . '/' . $filename);

      if (file_exists($url)) {
        $content = file_get_contents($url);
        // CSS内のパスを変更
        $content = preg_replace('/(?:\.\.\/images)/im', get_theme_file_uri('/images'), $content);
        return '<style type="text/css">' . $content . '</style>';
      }
    }

    return '';
  }

  /**
   * wp_dieのカスタムハンドラ
   *
   * @since 1.0
   * @see https://core.trac.wordpress.org/browser/trunk/src/wp-includes/functions.php#L2832
   *
   * @param string|WP_Error $message Error message or WP_Error object.
   * @param string          $title   Optional. Error title. Default empty.
   * @param string|array    $args    Optional. Arguments to control behavior. Default empty array.
   */
  public function die( $message, $title = '', $args = array() ) {
    $defaults = array( 'response' => 500 );
    $r = wp_parse_args($args, $defaults);
    $back_link = '';

    if ( function_exists( 'is_wp_error' ) && is_wp_error( $message ) ) {
      if ( empty( $title ) ) {
        $error_data = $message->get_error_data();
        if ( is_array( $error_data ) && isset( $error_data['title'] ) )
          $title = $error_data['title'];
      }
      $errors = $message->get_error_messages();
      switch ( count( $errors ) ) {
      case 0 :
        $message = '';
        break;
      case 1 :
        $message = "<p>{$errors[0]}</p>";
        break;
      default :
        $message = "<ul>\n\t\t<li>" . join( "</li>\n\t\t<li>", $errors ) . "</li>\n\t</ul>";
        break;
      }
    } elseif ( !empty($message)  ) {
      $message = "<p>$message</p>";
    }

    if ( isset( $r['back_link'] ) && $r['back_link'] ) {
      $back_link = "\n<p><a href='javascript:history.back()' class='back-link'>&laquo; 前のページに戻る</a></p>";
    }

    if ( ! did_action( 'admin_head' ) ) :
      if ( !headers_sent() ) {
        status_header( $r['response'] );
        nocache_headers();
        header( 'Content-Type: text/html; charset=utf-8' );
      }

      if ( empty($title) )
        $title =  'エラー – ' . get_bloginfo('name');

    ?>
    <!DOCTYPE html>
    <html xmlns="http://www.w3.org/1999/xhtml" <?php if ( function_exists( 'language_attributes' ) && function_exists( 'is_rtl' ) ) language_attributes(); else echo "dir='$text_direction'"; ?>>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <meta name="viewport" content="width=device-width">
    <?php echo $this->get_stylesheet() ?>
    <?php
    if ( function_exists( 'wp_no_robots' ) ) {
      wp_no_robots();
    }
    ?>
    <title><?php echo $title ?></title>
    </head>
    <body class="error-page">
      <header class="site-header" ref="header">
    		<h1 class="site-title"><span class="site-logo">
            <?php bloginfo( 'name' ); ?>
          </span>
      </h1>
      </header>
    <?php endif; // ! did_action( 'admin_head' ) ?>
    <div class="error-content">
			<img src="<?php print get_template_directory_uri() . '/images/page-not-found.png' ?>" width="100%" class="not-found-img" alt="お探しのページが見つかりませんでした">

      <div class="error-message">
        <?php echo $message; ?>
        <a href="<?php bloginfo('home') ?>" class="goto-home">トップページへ</a>
        <?php echo $back_link ?>
      </div>

    </div>

    </body>
    </html>
    <?php
    die();
  }
}
	<?php
	/**
	* 味気ないwp_dieの出力を変更する
	*/
	class CustomDie {

	public function __cosntruct() {
	}

	public function enable_custom_die() {
	add_filter( 'wp_die_handler', array($this, 'die_handler') );
	}

	public function die_handler($function){
	if(!is_admin()) {
	return array($this, 'die');
	}
	}

	/**
	* Get maintenance mode page css
	*
	* @since 1.0
	* @return string
	*/
	private function get_stylesheet() {
	$filename = apply_filters('maintenance_css_filename', '/css/maintenance.css');

	if (!validate_file($filename)) {
	$url = apply_filters('maintenance_css_url', get_stylesheet_directory() . '/' . $filename);

	if (file_exists($url)) {
	$content = file_get_contents($url);
	// CSS内のパスを変更
	$content = preg_replace('/(?:\.\.\/images)/im', get_theme_file_uri('/images'), $content);
	return '<style type="text/css">' . $content . '</style>';
	}
	}

	return '';
	}

	/**
	* wp_dieのカスタムハンドラ
	*
	* @since 1.0
	* @see https://core.trac.wordpress.org/browser/trunk/src/wp-includes/functions.php#L2832
	*
	* @param string\|WP_Error $message Error message or WP_Error object.
	* @param string $title Optional. Error title. Default empty.
	* @param string\|array $args Optional. Arguments to control behavior. Default empty array.
	*/
	public function die( $message, $title = '', $args = array() ) {
	$defaults = array( 'response' => 500 );
	$r = wp_parse_args($args, $defaults);
	$back_link = '';

	if ( function_exists( 'is_wp_error' ) && is_wp_error( $message ) ) {
	if ( empty( $title ) ) {
	$error_data = $message->get_error_data();
	if ( is_array( $error_data ) && isset( $error_data['title'] ) )
	$title = $error_data['title'];
	}
	$errors = $message->get_error_messages();
	switch ( count( $errors ) ) {
	case 0 :
	$message = '';
	break;
	case 1 :
	$message = "<p>{$errors[0]}</p>";
	break;
	default :
	$message = "<ul>\n\t\t<li>" . join( "</li>\n\t\t<li>", $errors ) . "</li>\n\t</ul>";
	break;
	}
	} elseif ( !empty($message) ) {
	$message = "<p>$message</p>";
	}

	if ( isset( $r['back_link'] ) && $r['back_link'] ) {
	$back_link = "\n<p><a href='javascript:history.back()' class='back-link'>« 前のページに戻る</a></p>";
	}

	if ( ! did_action( 'admin_head' ) ) :
	if ( !headers_sent() ) {
	status_header( $r['response'] );
	nocache_headers();
	header( 'Content-Type: text/html; charset=utf-8' );
	}

	if ( empty($title) )
	$title = 'エラー – ' . get_bloginfo('name');

	?>
	<!DOCTYPE html>
	<html xmlns="http://www.w3.org/1999/xhtml" <?php if ( function_exists( 'language_attributes' ) && function_exists( 'is_rtl' ) ) language_attributes(); else echo "dir='$text_direction'"; ?>>
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<meta name="viewport" content="width=device-width">
	<?php echo $this->get_stylesheet() ?>
	<?php
	if ( function_exists( 'wp_no_robots' ) ) {
	wp_no_robots();
	}
	?>
	<title><?php echo $title ?></title>
	</head>
	<body class="error-page">
	<header class="site-header" ref="header">
	<h1 class="site-title"><span class="site-logo">
	<?php bloginfo( 'name' ); ?>
	</span>
	</h1>
	</header>
	<?php endif; // ! did_action( 'admin_head' ) ?>
	<div class="error-content">
	<img src="<?php print get_template_directory_uri() . '/images/page-not-found.png' ?>" width="100%" class="not-found-img" alt="お探しのページが見つかりませんでした">

	<div class="error-message">
	<?php echo $message; ?>
	<a href="<?php bloginfo('home') ?>" class="goto-home">トップページへ</a>
	<?php echo $back_link ?>
	</div>

	</div>

	</body>
	</html>
	<?php
	die();
	}
	}