AWS CloudFormation: Need to install a new php version

I have a CloudFormation template that sets up a server with Apache and PHP.
For an example, look at this simple template that installs php and httpd.
https://s3.amazonaws.com/cloudformation-templates-us-east-1/WordPress_Single_Instance.template

The setup is done in the "AWS::CloudFormation::Init" section via the following snippet

            "packages" : {
              "yum" : {
                "php"        : [],
		"httpd"        : []
		}
            },

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The thing is that this method installs php 5.3.29, and I need at least 5.4.

According to documentation, the required version number can be included in the package description, so I tried this

"php"        : ["5.4"],

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and this

"php"        : ["54"],

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but nothing works. Specifying the version number causes php to not be installed at all, and ultimately to stack failure and rollback.

So how do I make CloudFormation install php 5.4?

I can modify the template to run an install command via the user-data, like this

yum -y install php54

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But it is rather inelegant.