Dissection of a XML-RPC Call - PHP

An XML-RPC call is sent from a client to a server via HTTP POST. This allows XML-RPC applications to work fairly easily behind firewalls, as port 80 is almost always open.

Here's a sample XML-RPC call:

POST xmlrpcexample.php HTTP/1.0
User-Agent: xmlrpc-epi-php/0.2 (PHP)
Host: localhost:80
Content-Type: text/xml
Content-length: 191
<?xml version='1.0' encoding="iso-8859-1" ?>
<methodCall>
<methodName>greeting</methodName>
<params>
<param>
<value>
<string>Lucas</string>
</value>
</param>
</params>
</methodCall>

The first part of the request is simply a standard HTML post request. It's the data sent in the body of the request that interests us.

The <methodCall> tags simply encapsulate the call, with all the parameters enclosed in <params> and each parameter enclosed in <param>.

Parameters are specified enclosed in tags that tell the application what type of parameter they are. In this case, "Lucas" is a string, so it is enclosed in <string>, but there are a lot more parameter types:

<i4> or <int>	four-byte signed integer	10
<boolean>	0 (false) or 1 (true)	1
<string>	ASCII string	Hello, DevShed!
<double>	double-precision signed floating point number	-21.2544
<dateTime.iso8601>	date/time	20011219T12:05:26
<base64>	base64-encoded binary	eW91IGNhbid0IHJlYWQgdGhpcyE=

In addition to the basic types, there are also <struct>s and <array>s, <struct>s containing any number of <member>s that consist of <name>s and <value>s (specified in the same manner as <param>s):

<struct>
<member>
<name>name</name>
<value>
<string>Lucas Marshall</string>
</value>
</member>
<member>
<name>age</name>
<value>
<i4>20</i4>
</value>
</member>
</struct>

and arrays merely containing any number of <value>s:

<array>
<value><i4>10</i4></value>
<value><i4>20</i4></value>
<value><i4>30</i4></value>
</array>

>>> More PHP Articles          >>> More By Lucas Marshall

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