arg_name:paramname:$maptype::php:`MongoDB\\BSON\\Javascript <mongodb-bson-javascript>`description:|A JavaScript function that associates or "maps" a value with a key and emitsthe key and value pair.interface:phpmethodoperation:~optional:false---arg_name:paramname:$reducetype::php:`MongoDB\\BSON\\Javascript <class.mongodb-bson-javascript>`description:|A JavaScript function that "reduces" to a single object all the valuesassociated with a particular key.interface:phpmethodoperation:~optional:false---arg_name:paramname:$outtype:string|documentdescription:|Specifies where to output the result of the map-reduce operation. You caneither output to a collection or return the result inline. On a primary memberof a replica set you can output either to a collection or inline, but on asecondary, only inline output is possible.interface:phpmethodoperation:~optional:false---source:file:apiargs-common-param.yamlref:$options...