Validates the theme requirements for WordPress version and PHP version.

Uses the information from `Requires at least` and `Requires PHP` headers
defined in the theme’s `style.css` file.

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( 'Error: 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( 'Error: 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( 'Error: Current WordPress version does not meet minimum requirements for %s.', 'theme' ),
				$theme->display( 'Name' )
			)
		);
	}

	return true;
}