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Types and Conversions

Some remote method calls require parameters. These are given to the call() method of Zend_XmlRpc_Client as an array in the second parameter. Each parameter may be given as either a native PHP type which will be automatically converted, or as an object representing a specific XML-RPC type (one of the Zend_XmlRpc_Value objects).

PHP Native Types as Parameters

Parameters may be passed to call() as native PHP variables, meaning as a String, Integer, Float, Boolean, Array, or an Object. In this case, each PHP native type will be auto-detected and converted into one of the XML-RPC types according to this table:

Table 174. PHP and XML-RPC Type Conversions

PHP Native Type XML-RPC Type
integer int
Zend_Crypt_Math_BigInteger i8
double double
boolean boolean
string string
null nil
array array
associative array struct
object array
Zend_Date dateTime.iso8601
DateTime dateTime.iso8601

What type do empty arrays get cast to?

Passing an empty array to an XML-RPC method is problematic, as it could represent either an array or a struct. Zend_XmlRpc_Client detects such conditions and makes a request to the server's system.methodSignature method to determine the appropriate XML-RPC type to cast to.

However, this in itself can lead to issues. First off, servers that do not support system.methodSignature will log failed requests, and Zend_XmlRpc_Client will resort to casting the value to an XML-RPC array type. Additionally, this means that any call with array arguments will result in an additional call to the remote server.

To disable the lookup entirely, you can call the setSkipSystemLookup() method prior to making your XML-RPC call:

$result $client->call('', array(array()));

Zend_XmlRpc_Value Objects as Parameters

Parameters may also be created as Zend_XmlRpc_Value instances to specify an exact XML-RPC type. The primary reasons for doing this are:

  • When you want to make sure the correct parameter type is passed to the procedure (i.e. the procedure requires an integer and you may get it from a database as a string)

  • When the procedure requires base64 or dateTime.iso8601 type (which doesn't exists as a PHP native type)

  • When auto-conversion may fail (i.e. you want to pass an empty XML-RPC struct as a parameter. Empty structs are represented as empty arrays in PHP but, if you give an empty array as a parameter it will be auto-converted to an XML-RPC array since it's not an associative array)

There are two ways to create a Zend_XmlRpc_Value object: instantiate one of the Zend_XmlRpc_Value subclasses directly, or use the static factory method Zend_XmlRpc_Value::getXmlRpcValue().

Table 175. Zend_XmlRpc_Value Objects for XML-RPC Types

XML-RPC Type Zend_XmlRpc_Value Constant Zend_XmlRpc_Value Object
int Zend_XmlRpc_Value::XMLRPC_TYPE_INTEGER Zend_XmlRpc_Value_Integer
i8 Zend_XmlRpc_Value::XMLRPC_TYPE_I8 Zend_XmlRpc_Value_BigInteger
ex:i8 Zend_XmlRpc_Value::XMLRPC_TYPE_APACHEI8 Zend_XmlRpc_Value_BigInteger
double Zend_XmlRpc_Value::XMLRPC_TYPE_DOUBLE Zend_XmlRpc_Value_Double
boolean Zend_XmlRpc_Value::XMLRPC_TYPE_BOOLEAN Zend_XmlRpc_Value_Boolean
string Zend_XmlRpc_Value::XMLRPC_TYPE_STRING Zend_XmlRpc_Value_String
nil Zend_XmlRpc_Value::XMLRPC_TYPE_NIL Zend_XmlRpc_Value_Nil
ex:nil Zend_XmlRpc_Value::XMLRPC_TYPE_APACHENIL Zend_XmlRpc_Value_Nil
base64 Zend_XmlRpc_Value::XMLRPC_TYPE_BASE64 Zend_XmlRpc_Value_Base64
dateTime.iso8601 Zend_XmlRpc_Value::XMLRPC_TYPE_DATETIME Zend_XmlRpc_Value_DateTime
array Zend_XmlRpc_Value::XMLRPC_TYPE_ARRAY Zend_XmlRpc_Value_Array
struct Zend_XmlRpc_Value::XMLRPC_TYPE_STRUCT Zend_XmlRpc_Value_Struct

Automatic Conversion

When building a new Zend_XmlRpc_Value object, its value is set by a PHP type. The PHP type will be converted to the specified type using PHP casting. For example, if a string is given as a value to the Zend_XmlRpc_Value_Integer object, it will be converted using (int)$value.

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