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 	$message = sprintf( __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ), $GLOBALS['wp_version'] );

    38 	printf( '<div class="error"><p>%s</p></div>', $message );

    39 }

    40 

    41 /**

    42  * Prevent the Customizer from being loaded on WordPress versions prior to 4.1.

    43  *

    44  * @since Twenty Fifteen 1.0

    45  */

    46 function twentyfifteen_customize() {

    47 	wp_die( sprintf( __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ), $GLOBALS['wp_version'] ), '', array(

    48 		'back_link' => true,

    49 	) );

    50 }

    51 add_action( 'load-customize.php', 'twentyfifteen_customize' );

    52 

    53 /**

    54  * Prevent the Theme Preview from being loaded on WordPress versions prior to 4.1.

    55  *

    56  * @since Twenty Fifteen 1.0

    57  */

    58 function twentyfifteen_preview() {

    59 	if ( isset( $_GET['preview'] ) ) {

    60 		wp_die( sprintf( __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ), $GLOBALS['wp_version'] ) );

    61 	}

    62 }

    63 add_action( 'template_redirect', 'twentyfifteen_preview' );