validate_theme_requirements()

validate_theme_requirements( string $stylesheet ): true|WP_Error

function validate_theme_requirements( $stylesheet ) {
	$theme = wp_get_theme( $stylesheet );

	$requirements = array(
		'requires'     => ! empty( $theme->get( 'RequiresWP' ) ) ? $theme->get( 'RequiresWP' ) : '',
		'requires_php' => ! empty( $theme->get( 'RequiresPHP' ) ) ? $theme->get( 'RequiresPHP' ) : '',
	);

	$compatible_wp  = is_wp_version_compatible( $requirements['requires'] );
	$compatible_php = is_php_version_compatible( $requirements['requires_php'] );

	if ( ! $compatible_wp && ! $compatible_php ) {
		return new WP_Error(
			'theme_wp_php_incompatible',
			sprintf(
				/* translators: %s: Theme name. */
				_x( '<strong>Error:</strong> Current WordPress and PHP versions do not meet minimum requirements for %s.', 'theme' ),
				$theme->display( 'Name' )
			)
		);
	} elseif ( ! $compatible_php ) {
		return new WP_Error(
			'theme_php_incompatible',
			sprintf(
				/* translators: %s: Theme name. */
				_x( '<strong>Error:</strong> Current PHP version does not meet minimum requirements for %s.', 'theme' ),
				$theme->display( 'Name' )
			)
		);
	} elseif ( ! $compatible_wp ) {
		return new WP_Error(
			'theme_wp_incompatible',
			sprintf(
				/* translators: %s: Theme name. */
				_x( '<strong>Error:</strong> Current WordPress version does not meet minimum requirements for %s.', 'theme' ),
				$theme->display( 'Name' )
			)
		);
	}

	/**
	 * Filters the theme requirement validation response.
	 *
	 * If a theme fails due to a Core-provided validation (incompatible WP, PHP versions), this
	 * filter will not fire. A WP_Error response will already be returned.
	 *
	 * This filter is intended to add additional validation steps by site administrators.
	 *
	 * @since 6.9.0
	 *
	 * @param bool|WP_Error $met_requirements True if the theme meets requirements, WP_Error if not.
	 * @param string $stylesheet Directory name for the theme.
	 */
	return apply_filters( 'validate_theme_requirements', true, $stylesheet );
}