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function is not described

filter_default_option() WP 4.7.0

Filter the default value for the option.

For settings which register a default setting in register_setting(), this function is added as a filter to default_option_{$option}.

No Hooks.

Return

Mixed. Filtered default value.

Usage

filter_default_option( $default, $option, $passed_default );
$default(mixed) (required)
Existing default value to return.
$option(string) (required)
Option name.
$passed_default(true/false) (required)
Was get_option() passed a default value?

Code of filter default option: wp-includes/option.php WP 5.2.1

<?php
function filter_default_option( $default, $option, $passed_default ) {
	if ( $passed_default ) {
		return $default;
	}

	$registered = get_registered_settings();
	if ( empty( $registered[ $option ] ) ) {
		return $default;
	}

	return $registered[ $option ]['default'];
}