I want to upload the pcap file through php Web-Form application, after that i want to process that file and convert that file into csv?

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That seems like a good task for tshark

Using Wiresharks tshark to Create a CSV File

The only way to do this is to link the dissection engine directly into your program and handle the capture file processing yourself. This would require you to use internal interfaces which are not documented, nor supported, nor constant. Also this means that the GPL will apply to your code, since the Wireshark code is covered by that. So although theoretically possible, you are on your own, as this is not supported use of Wireshark code.