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Function Reference/flush rewrite rules

Description

Remove rewrite rules and then recreate rewrite rules.

This function is useful when used with custom post types as it allows for automatic flushing of the WordPress rewrite rules (usually needs to be done manually for new custom post types). However, this is an expensive operation so it should only be used when absolutely necessary. See Usage section for more details.

Usage

Important:

  • Flushing the rewrite rules is an expensive operation, there are tutorials and examples that suggest executing it on the 'init' hook. This is bad practice.
  • Flush rules only on activation or deactivation, or when you know that the rewrite rules need to be changed (e.g. the addition of a new taxonomy or post type in your code). Don't do it on any other hook. More detail information in the comments on WP Engineer's post: Custom Post Type and Permalink
  • Make sure custom post types and taxonomies are properly registered before flushing rewrite rules, especially during plugin activation: Activation Checklist for WordPress Plugin Developers

<?php flush_rewrite_rules$hard ); ?>

Parameters

$hard
(boolean) (optional) Whether to update .htaccess (hard flush) or just update rewrite_rules transient (soft flush).
Default: true (hard flush)

Examples

This is how you would flush rewrite rules when a plugin is activated or deactivated:

function myplugin_activate() {
	// register taxonomies/post types here
	flush_rewrite_rules();
}

register_activation_hook( __FILE__, 'myplugin_activate' );

function myplugin_deactivate() {
	flush_rewrite_rules();
}
register_deactivation_hook( __FILE__, 'myplugin_deactivate' );

This is how you would flush rules on theme activation:

/* Flush rewrite rules for custom post types. */
add_action( 'after_switch_theme', 'bt_flush_rewrite_rules' );

/* Flush your rewrite rules */
function bt_flush_rewrite_rules() {
     flush_rewrite_rules();
}

If you're developing a theme, while building it you can use this snippet of code that will flush rewrite rules when the file containing it is changed, or every 48 hours:

// do not use on live/production servers
add_action( 'init','maybe_rewrite_rules' );
function maybe_rewrite_rules() {

	$ver = filemtime( __FILE__ ); // Get the file time for this file as the version number
	$defaults = array( 'version' => 0, 'time' => time() );
	$r = wp_parse_args( get_option( __CLASS__ . '_flush', array() ), $defaults );

	if ( $r['version'] != $ver || $r['time'] + 172800 < time() ) { // Flush if ver changes or if 48hrs has passed.
		flush_rewrite_rules();
		// trace( 'flushed' );
		$args = array( 'version' => $ver, 'time' => time() );
		if ( ! update_option( __CLASS__ . '_flush', $args ) )
			add_option( __CLASS__ . '_flush', $args );
	}

}

Change Log

Since: 3.0

Source File

flush_rewrite_rules() is located in wp-includes/rewrite.php

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