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   1  <?php
   2  /**
   3   * Twenty Fifteen back compat functionality
   4   *
   5   * Prevents Twenty Fifteen from running on WordPress versions prior to 4.1,
   6   * since this theme is not meant to be backward compatible beyond that and
   7   * relies on many newer functions and markup changes introduced in 4.1.
   8   *
   9   * @package WordPress
  10   * @subpackage Twenty_Fifteen
  11   * @since Twenty Fifteen 1.0
  12   */
  13  
  14  /**
  15   * Prevent switching to Twenty Fifteen on old versions of WordPress.
  16   *
  17   * Switches to the default theme.
  18   *
  19   * @since Twenty Fifteen 1.0
  20   */
  21  function twentyfifteen_switch_theme() {
  22      switch_theme( WP_DEFAULT_THEME, WP_DEFAULT_THEME );
  23      unset( $_GET['activated'] );
  24      add_action( 'admin_notices', 'twentyfifteen_upgrade_notice' );
  25  }
  26  add_action( 'after_switch_theme', 'twentyfifteen_switch_theme' );
  27  
  28  /**
  29   * Add message for unsuccessful theme switch.
  30   *
  31   * Prints an update nag after an unsuccessful attempt to switch to
  32   * Twenty Fifteen on WordPress versions prior to 4.1.
  33   *
  34   * @since Twenty Fifteen 1.0
  35   */
  36  function twentyfifteen_upgrade_notice() {
  37      printf(
  38          '<div class="error"><p>%s</p></div>',
  39          sprintf(
  40              /* translators: %s: WordPress version. */
  41              __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ),
  42              $GLOBALS['wp_version']
  43          )
  44      );
  45  }
  46  
  47  /**
  48   * Prevent the Customizer from being loaded on WordPress versions prior to 4.1.
  49   *
  50   * @since Twenty Fifteen 1.0
  51   */
  52  function twentyfifteen_customize() {
  53      wp_die(
  54          sprintf(
  55              /* translators: %s: WordPress version. */
  56              __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ),
  57              $GLOBALS['wp_version']
  58          ),
  59          '',
  60          array(
  61              'back_link' => true,
  62          )
  63      );
  64  }
  65  add_action( 'load-customize.php', 'twentyfifteen_customize' );
  66  
  67  /**
  68   * Prevent the Theme Preview from being loaded on WordPress versions prior to 4.1.
  69   *
  70   * @since Twenty Fifteen 1.0
  71   */
  72  function twentyfifteen_preview() {
  73      if ( isset( $_GET['preview'] ) ) {
  74          wp_die(
  75              sprintf(
  76                  /* translators: %s: WordPress version. */
  77                  __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ),
  78                  $GLOBALS['wp_version']
  79              )
  80          );
  81      }
  82  }
  83  add_action( 'template_redirect', 'twentyfifteen_preview' );