Which keyword is best for keywords ranking on search engine?

I have keywords with two phase, one ranking on in 100 while second one is ranking 500+.

Keywords is look like php programmer and php programmers, difference is only “s” at end of keywords.

php programmer - 100
php programmers – 500

Which keyword, I have to target for seo, so I can get my both keywords ranking on search engine.

Thanks!

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