Determines whether WordPress is already installed.

Description Description

The cache will be checked first. If you have a cache plugin, which saves the cache values, then this will work. If you use the default WordPress cache, and the database goes away, then you might have problems.

Checks for the ‘siteurl’ option for whether WordPress is installed.

For more information on this and similar theme functions, check out the Conditional Tags article in the Theme Developer Handbook.

Return Return

(bool) Whether the site is already installed.

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Source Source

File: wp-includes/functions.php

function is_blog_installed() {
	global $wpdb;

	 * Check cache first. If options table goes away and we have true
	 * cached, oh well.
	if ( wp_cache_get( 'is_blog_installed' ) )
		return true;

	$suppress = $wpdb->suppress_errors();
	if ( ! wp_installing() ) {
		$alloptions = wp_load_alloptions();
	// If siteurl is not set to autoload, check it specifically
	if ( !isset( $alloptions['siteurl'] ) )
		$installed = $wpdb->get_var( "SELECT option_value FROM $wpdb->options WHERE option_name = 'siteurl'" );
		$installed = $alloptions['siteurl'];
	$wpdb->suppress_errors( $suppress );

	$installed = !empty( $installed );
	wp_cache_set( 'is_blog_installed', $installed );

	if ( $installed )
		return true;

	// If visiting repair.php, return true and let it take over.
	if ( defined( 'WP_REPAIRING' ) )
		return true;

	$suppress = $wpdb->suppress_errors();

	 * Loop over the WP tables. If none exist, then scratch installation is allowed.
	 * If one or more exist, suggest table repair since we got here because the
	 * options table could not be accessed.
	$wp_tables = $wpdb->tables();
	foreach ( $wp_tables as $table ) {
		// The existence of custom user tables shouldn't suggest an insane state or prevent a clean installation.
		if ( defined( 'CUSTOM_USER_TABLE' ) && CUSTOM_USER_TABLE == $table )
		if ( defined( 'CUSTOM_USER_META_TABLE' ) && CUSTOM_USER_META_TABLE == $table )

		if ( ! $wpdb->get_results( "DESCRIBE $table;" ) )

		// One or more tables exist. We are insane.


		// Die with a DB error.
		$wpdb->error = sprintf(
			/* translators: %s: database repair URL */
			__( 'One or more database tables are unavailable. The database may need to be <a href="%s">repaired</a>.' ),


	$wpdb->suppress_errors( $suppress );

	wp_cache_set( 'is_blog_installed', false );

	return false;

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Changelog Changelog

Version Description
2.1.0 Introduced.

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