Here is the test outline for Brainbench's PHP4 test.
Advanced PHP 4
Session Handling
Web-Based Administration
Basics
Configuration
Installation
Logging
UNIX
Windows
Database
Basic SQL and Installation
Creating and Populating Tables
Functions
Database Connections
MySQL
Oracle
Other Sources
PostgreSQL
SQL Server
Essentials
Authentication
Cookies/User Tracking
E-Commerce
Security
Functions
Array
File
Graphics
HTTP
IMAP
LDAP
Math
Networking
Other Functions
PDF
String
Language
Basics
Control Structures
Operators
Syntax
Variable
It will really only matter if the employer knows what is covered on the test and needs those skills. Otherwise, best to show examples of your work. Have live site demos of PHP apps that you have written to show functionaility and of course, show them some code samples.
I've interviewed for many positions for php where nobody asked me for code samples and they didn't really look at my sites. They asked questions to assess my skills so you may want to make sure you know your stuff in your head. I got hired by my current employer based on my resume and my interview, they never looked at previous work or code.