The first issue you might find is to actually find a proper software architect, if your project is porn related. Like mentioned by edgeprod, programmers that are of senior level have more work that they can handle. That means that they choose what benefits them the most, in salary and in "fun at work".
Now, if your project is adult related, most senior software engineer won't touch your project. This is a problem most big adult related companies are facing.
But, if you are paying enough, you might be able to get a few. However, you need to know how to spot a senior software architect vs someone that thinks he is senior.
The best bet would be to talk about design patterns. If he can't name and explain the obvious ones, stay away from the guys. (
http://en.wikipedia.org/wiki/Software_design_pattern )
Then, asks him questions related to Dependency Injection (
http://en.wikipedia.org/wiki/Dependency_injection ). If he can't answer, he is not a senior.
Then, asks him how he tests his softwares. If he is not unit & infrastructure testing all his code or if he's not creating reports related to his code's tests coverage, then he is not a senior.
Then, ask him questions about continuous integration (
http://en.wikipedia.org/wiki/Continuous_integration ). If he can't answer you, don't bother, he is not a senior.
Ask him about the books (related to software engineering) he reads and enjoys. Then, have a look on amazon and see if the books are related to any of the subjects mentioned above. If not, don't bother, he is not a senior.
Then, asks him about creating a RESTful API to encapsulate all your business logic, so that you can easily and quickly create sites, on different platforms, without re-writing all your business logic everywhere (
http://en.wikipedia.org/wiki/Represe...state_transfer ). If the guy doesn't know how to WRITE RESTful API's CORRECTLY, don't bother, he is not a senior.
That being said, if the guy is really a senior, expect to pay around 150k$ for his work. If quality is very important for you, you should invest in a senior software architect that write code.
However, if you need to create projects quickly and you are in the "we create demos and quick projects to test the water" mode, then go with a cheap hacker that can "get the job done". Then, when the project makes money and you need it to work properly, invest in a senior software architect to re-write your whole platform. Then, you will reach quality.
For a hacker that can "get the job done", the salary is around 60k-80k here in Montreal. These people normally have around 2-5 years of experience. However, some people stays juniors all their life.
For junior developers, the salary is around 35k-50k here in Montreal. Junior are basically developers that just got out of school or have less than 1-2 years of experience. However, some people stays juniors all their life.
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For the people that care...
You can unit test your code in php using PHPUnit:
http://www.phpunit.de/manual/current/en/
Selenium is used to do Infrastructure testing:
http://seleniumhq.org/
Jenkins is a continuous integration platform:
http://jenkins-php.org/
Jenkins can be used with PHP:
http://jenkins-php.org/
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Good luck finding someone!