WordPress at a glance
function is not described

wp_get_environment_type() WP 5.5.0

Retrieves the current environment type.

The type can be set via the WP_ENVIRONMENT_TYPE global system variable, or a constant of the same name.

Possible values are 'local', 'development', 'staging', and 'production'. If not set, the type defaults to 'production'.

No Hooks.

Return

String. The current environment type.

Usage

wp_get_environment_type();

Changelog

Since 5.5.0 Introduced.
Since 5.5.1 Added the 'local' type.
Since 5.5.1 Removed the ability to alter the list of types.

Code of wp_get_environment_type() WP 5.7.1

<?php
function wp_get_environment_type() {
	static $current_env = '';

	if ( $current_env ) {
		return $current_env;
	}

	$wp_environments = array(
		'local',
		'development',
		'staging',
		'production',
	);

	// Add a note about the deprecated WP_ENVIRONMENT_TYPES constant.
	if ( defined( 'WP_ENVIRONMENT_TYPES' ) && function_exists( '_deprecated_argument' ) ) {
		if ( function_exists( '__' ) ) {
			/* translators: %s: WP_ENVIRONMENT_TYPES */
			$message = sprintf( __( 'The %s constant is no longer supported.' ), 'WP_ENVIRONMENT_TYPES' );
		} else {
			$message = sprintf( 'The %s constant is no longer supported.', 'WP_ENVIRONMENT_TYPES' );
		}

		_deprecated_argument(
			'define()',
			'5.5.1',
			$message
		);
	}

	// Check if the environment variable has been set, if `getenv` is available on the system.
	if ( function_exists( 'getenv' ) ) {
		$has_env = getenv( 'WP_ENVIRONMENT_TYPE' );
		if ( false !== $has_env ) {
			$current_env = $has_env;
		}
	}

	// Fetch the environment from a constant, this overrides the global system variable.
	if ( defined( 'WP_ENVIRONMENT_TYPE' ) ) {
		$current_env = WP_ENVIRONMENT_TYPE;
	}

	// Make sure the environment is an allowed one, and not accidentally set to an invalid value.
	if ( ! in_array( $current_env, $wp_environments, true ) ) {
		$current_env = 'production';
	}

	return $current_env;
}