I have added adsense in one of my blog http://my-source-codes.blogspot.com.This blog is having two topics mostly about php scrpts developements and windows mobile application tips tricks etc.So problem is all of my php post has not relevant ads.Most of ads on php post pages are about hosting company.I have try section targeting.I also try to optimize keyword frequency but the adsense ads are not relevant to my post. Can anyone help me!
Actually 'php' would be a keyword that hosting companies are buying. When you want a webhost, you do want them to have php installed. I honestly can't say I've ever seen an ad *for* php of any kind ... php is free after all, and people looking for php tips are already using it. You're proabably already getting the most relevant ads. I see ads for captchas and payment gateways not hosting, both of those are relevant. Edit: the english on your site is pretty poor and the content is a bit thin on the ground too, you might want to do some proofreading and pad your posts out a bit.
On your Adsense Setup, there is Competitive Ad Filter. You can use this to exclude the current ads which is not related on your site. Also this Competitive Ad Filter will help you to filter low paying ads. Another thing is that, you need to optimize your articles to target your desired niche such as PHP.