Api Integration Required "Expert Only"

Hello, we have parcel delivery website and we need to integrate the parcel force api in order to generated shipping labels dynamically at the time of order is being done by customer. We will provide you all the documentation regarding the api. Our site has been built in PHP and mysql. I will provide you the site url to the interested applicant via pmb. My budget for this project is £20 as It will not take so much time to complete the task who is experienced in api integration. Our programmer has already resolved almost 80% of the api and is receiving response from their server as well but can’t print the data in the browser when we have decoded the response as base64_decode? We save the decoded data in a pdf file but every time it is blank. We have other 2 issues as such which need to be resolved. It wont take time for an expert and hence need quick solution. Thanks.