i am a student of wen developer. give me some knowledge about this field
This question is a bit too vague to get any reasonable answer.The first place to look to learn about PHP is the manual:-http://php.net/manual/en/
In the forums it is better to ask a more specific question as this subject is far too wide reaching.
i love designing included html css but php is bit difficult for me .due to its coding part
You should read this book:
PHP has many uses. To focus this topic on something more specific; can you explain what it is you intend to achieve with PHP?
Some bare bone basic knowledge from someone who has been in this industry for a decade - you should learn some basic grammar. Just saying...