The behaviour of these functions is affected by settings in php.ini.
Here's a short explanation of the configuration directives.
Enables or disables the WSDL caching feature.
Sets the directory name where the SOAP extension will put cache files.
Sets the number of seconds (time to live) that cached files will be used instead of the originals.
If soap.wsdl_cache_enabled is on, this setting determines the type of caching. It can be any of: WSDL_CACHE_NONE (0), WSDL_CACHE_DISK (1), WSDL_CACHE_MEMORY (2) or WSDL_CACHE_BOTH (3). This can also be set via the options array in the SoapClient or SoapServer constructor.
Maximum number of in-memory cached WSDL files. Adding further files into a full memory cache will delete the oldest files from it.