code: public function setPermissionSet($value = array())
  	{
  		foreach ($value as $url) {
  			if (strpos($url, $this->accountName) === false) {
  				throw new Exception('The permission set can only contain URLs for the account name specified in the Credentials_SharedAccessSignature instance.');
  			}
  		}
  	    $this->permissionSet = $value;
  	}
docs: Set permisison set
  
  Warning: fine-grained permissions should be added prior to coarse-grained permissions.
  For example: first add blob permissions, end with container-wide permissions.
  
  Warning: the signed access signature URL must match the account name of the
  Credentials_Credentials_SharedAccessSignature instance
  
  @param  array $value Permission set
  @return void