wp-includes/class-wpdb.php:2116Checks that the connection to the database is still up. If not, try to reconnect.
$allow_bailbooloptionaltruebool|void public function check_connection( $allow_bail = true ) { // Check if the connection is alive. if ( ! empty( $this->dbh ) && mysqli_query( $this->dbh, 'DO 1' ) !== false ) { return true; } $error_reporting = false; // Disable warnings, as we don't want to see a multitude of "unable to connect" messages. if ( WP_DEBUG ) { $error_reporting = error_reporting(); error_reporting( $error_reporting & ~E_WARNING ); } for ( $tries = 1; $tries <= $this->reconnect_retries; $tries++ ) { /* * On the last try, re-enable warnings. We want to see a single instance * of the "unable to connect" message on the bail() screen, if it appears. */ if ( $this->reconnect_retries === $tries && WP_DEBUG ) { error_reporting( $error_reporting ); } if ( $this->db_connect( false ) ) { if ( $error_reporting ) { error_reporting( $error_reporting ); } return true; } sleep( 1 ); } /* * If template_redirect has already happened, it's too late for wp_die()/dead_db(). * Let's just return and hope for the best. */ if ( did_action( 'template_redirect' ) ) { return false; } if ( ! $allow_bail ) { return false; } wp_load_translations_early(); $message = '<h1>' . __( 'Error reconnecting to the database' ) . "</h1>\n"; $message .= '<p>' . sprintf( /* translators: %s: Database host. */ __( 'This means that the contact with the database server at %s was lost. This could mean your host’s database server is down.' ), '<code>' . htmlspecialchars( $this->dbhost, ENT_QUOTES ) . '</code>' ) . "</p>\n"; $message .= "<ul>\n"; $message .= '<li>' . __( 'Are you sure the database server is running?' ) . "</li>\n"; $message .= '<li>' . __( 'Are you sure the database server is not under particularly heavy load?' ) . "</li>\n"; $message .= "</ul>\n"; $message .= '<p>' . sprintf( /* translators: %s: Support forums URL. */ __( 'If you are unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href="%s">WordPress support forums</a>.' ), __( 'https://wordpress.org/support/forums/' ) ) . "</p>\n"; // We weren't able to reconnect, so we better bail. $this->bail( $message, 'db_connect_fail' ); /* * Call dead_db() if bail didn't die, because this database is no more. * It has ceased to be (at least temporarily). */ dead_db(); }Introduced in 3.9.0. One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
bool|void to bool.verified against sourcesrc/wp-includes/class-wpdb.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.