is_blog_installed() WordPress Function

The is_blog_installed() function in WordPress checks whether a blog is installed. This function is used by the installation process and during upgrade. It is also used by the wp-admin/includes/upgrade.php script.

is_blog_installed() #

Determines whether WordPress is already installed.

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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.

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Return

(bool) Whether the site is already installed.

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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'" );
    } else {
        $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 unwise state or prevent a clean installation.
        if ( defined( 'CUSTOM_USER_TABLE' ) && CUSTOM_USER_TABLE == $table ) {
            continue;
        }
        if ( defined( 'CUSTOM_USER_META_TABLE' ) && CUSTOM_USER_META_TABLE == $table ) {
            continue;
        }
 
        $described_table = $wpdb->get_results( "DESCRIBE $table;" );
        if (
            ( ! $described_table && empty( $wpdb->last_error ) ) ||
            ( is_array( $described_table ) && 0 === count( $described_table ) )
        ) {
            continue;
        }
 
        // One or more tables exist. This is not good.
 
        wp_load_translations_early();
 
        // 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>.' ),
            'maint/repair.php?referrer=is_blog_installed'
        );
 
        dead_db();
    }
 
    $wpdb->suppress_errors( $suppress );
 
    wp_cache_set( 'is_blog_installed', false );
 
    return false;
}

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Uses

Uses
Uses	Description
wp-includes/load.php:wp_installing()	Check or set whether WordPress is in “installation” mode.
wp-includes/cache.php:wp_cache_get()	Retrieves the cache contents from the cache by key and group.
wp-includes/cache.php:wp_cache_set()	Saves the data to the cache.
wp-includes/l10n.php:__()	Retrieve the translation of $text.
wp-includes/load.php:wp_load_translations_early()	Attempt an early load of translations.
wp-includes/functions.php:dead_db()	Load custom DB error or display WordPress DB error.
wp-includes/option.php:wp_load_alloptions()	Loads and caches all autoloaded options, if available or all options.
wp-includes/wp-db.php:wpdb::get_var()	Retrieves one variable from the database.
wp-includes/wp-db.php:wpdb::get_results()	Retrieves an entire SQL result set from the database (i.e., many rows).
wp-includes/wp-db.php:wpdb::suppress_errors()	Enables or disables suppressing of database errors.
wp-includes/wp-db.php:wpdb::tables()	Returns an array of WordPress tables.

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Used By

Used By
Used By	Description
wp-admin/includes/upgrade.php:wp_upgrade()	Runs WordPress Upgrade functions.
wp-includes/load.php:wp_not_installed()	Redirect to the installer if WordPress is not installed.
wp-includes/widgets.php:wp_widgets_init()	Registers all of the default WordPress widgets on startup.

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Changelog

Changelog
Version	Description
2.1.0	Introduced.

is_blog_installed() WordPress Function