One thing I detest about job interviews is that you have to lie even if you really mean to be honest. You have to lie in order to convey your true skill properly. (Not that I have extensive experience on job interviews, but this is from what I have gathered.)
For example, suppose that you are an experienced programmer and have a good grasp of how imperative/OO languages (either compiled or scripting) work, and have extensive experience on some languages, but only a very modest understanding of PHP in particular: You know the basics, you have perhaps written a hundred of lines of it in total, but you know how it works and what it offers. Most importantly, if you had to, you could quickly learn to use it proficiently and competently.
However, job interviews don't generally ask you that. Instead, they ask you how much you have programmed in PHP.
You have two choices: Tell the truth, or "stretch it a bit".
If you tell them that you have only minimal experience of PHP in particular, they will probably mark you as not a very good candidate for a PHP programming job. Your assurances that you can learn the language quickly and that's not just BS will probably not help much.
The other possibility is to outright lie: You can claim that you have programmed in PHP quite a lot.
In a sense you are not "lying" per se. Rather, you are answering the question that they really want to ask, rather than the question they think they want to ask. What they really want to know is how easily you could start programming in PHP, not how much you have programmed with it in the past. (Of course having a lot of experience in PHP programming always helps, I'm not saying it doesn't. However, even more important is how much programming experience in that type of language you have overall, not how much you have in PHP in particular.)
However, in order to convey your true expertise you have to lie. The bad thing about this is that you can get caught redhanded. If they start asking some minutia about PHP you might not know the answers on the spot, and you will end up looking like an opportunistic liar.
They might well end up hiring someone who has programmed more in PHP (or at least claims to be) but who's not very good at it.