On this page:
Inheritance Hierarchy for Exceptions in PHP
The mapping for exceptions is based on the inheritance hierarchy shown below:
Inheritance structure for Ice exceptions.
The ancestor of all exceptions is
Exception, from which
Ice_Exception is derived.
Ice_UserException are derived from
Ice_Exception and form the base for all run-time and user exceptions.
PHP Mapping for User Exceptions
Here is a fragment of the Slice definition for our world time server once more:
These exception definitions map to the abbreviated PHP class definitions shown below:
Each Slice exception is mapped to a PHP class with the same name. The inheritance structure of the Slice exceptions is preserved for the generated classes, so
BadZoneName inherit from
Each exception member corresponds to an instance variable of the instance, which the constructor initializes to a default value appropriate for its type:
|Data Member Type||Default Value|
|First enumerator in enumeration|
You can also declare different default values for members of primitive and enumerated types. For derived exceptions, the constructor has one parameter for each of the base exception's data members, plus one parameter for each of the derived exception's data members, in base-to-derived order. As an example, although
BadZoneName do not declare data members, their constructors still accept a value for the inherited data member
reason in order to pass it to the constructor of the base exception
Each exception also defines the
ice_name method to return the exception's type name, as well as the
__toString magic method to return a stringified representation of the exception and its members.
All user exceptions are derived from the base class
Ice_UserException. This allows you to catch all user exceptions generically by installing a handler for
Ice_UserException. Similarly, you can catch all Ice run-time exceptions with a handler for
Ice_LocalException, and you can catch all Ice exceptions with a handler for
Optional Data Members
Optional data members use the same mapping as required data members, but an optional data member can also be set to the marker value
Ice_Unset to indicate that the member is unset. A well-behaved program must compare an optional data member to
Ice_Unset before using the member's value:
Ice_Unset marker value has different semantics than
null is a legal value for certain Slice types, the Ice run time requires a separate marker value so that it can determine whether an optional value is set. An optional value set to
null is considered to be set. If you need to distinguish between an unset value and a value set to
null, you can do so as follows:
PHP Mapping for Run-Time Exceptions
The Ice run time throws run-time exceptions for a number of pre-defined error conditions. All run-time exceptions directly or indirectly derive from
Ice_LocalException (which, in turn, derives from
By catching exceptions at the appropriate point in the inheritance hierarchy, you can handle exceptions according to the category of error they indicate:
This is the root of the inheritance tree for run-time exceptions.
This is the root of the inheritance tree for user exceptions.
This is the base exception for both operation-invocation and connection-establishment timeouts.
This exception is raised when the initial attempt to establish a connection to a server times out.
Ice_ConnectTimeoutException can be handled as
You will probably have little need to catch run-time exceptions as their most-derived type and instead catch them as
Ice_LocalException; the fine-grained error handling offered by the remainder of the hierarchy is of interest mainly in the implementation of the Ice run time. Exceptions to this rule are the exceptions related to facet and object life cycles, which you may want to catch explicitly. These exceptions are