Sets the external entity reference handler function for the XML parser
handler is a string containing the name of a
function that must exist when xml_parse() is called
The function named by handler must accept
five parameters, and should return an integer value.If the
value returned from the handler is
FALSE (which it will be if no
value is returned), the XML parser will stop parsing and
xml_get_error_code() will return
The first parameter,
parser, is a
reference to the XML parser calling the handler.
The second parameter, open_entity_names, is a
space-separated list of the names of the entities that are open for
the parse of this entity (including the name of the referenced
This is the base for resolving the system identifier
(system_id) of the external entity.Currently
this parameter will always be set to an empty string.
The fourth parameter, system_id, is the
system identifier as specified in the entity declaration.
The fifth parameter, public_id, is the
public identifier as specified in the entity declaration, or
an empty string if none was specified; the whitespace in the
public identifier will have been normalized as required by
the XML spec.
If a handler function is set to an empty string, or
FALSE, the handler
in question is disabled.
Instead of a function name, an
array containing an object reference and a method name can also be
TRUE on success or
FALSE on failure.