Build a working PHP upload method for pre-existing website

I need someone to create a custom PHP upload image method. Basically people will go there, upload an image to the server.. then when image is upload, upload that image to the server to overwrite existing image. This is the hard part, I don't know how its done exactly. I know a few people have found methods already but won't share the method. I know with the other people that have already found methods it works like this. They set up a page that is a php upload method.. You goto the page, select a file to upload and upload it to the pages server. The server verfies that the image is no larger than 512 x 512 and no bigger than 1MB, if it passes this test, it goes to the next page showing the image, with an entry bar underneath to type in the crew address that the emblem is uploading to. When you put in the crew link, it checks to make sure that the crew is set to open (this is the key to being able to exploit the page and upload an image, their crew must be set to open which much somehow change the file permissions.. the website the upload needs to goto is [login to view URL] but it would go to a crew.. an example of a crew on there is here [login to view URL] this upload method must work externally from a seperate domain. some strings of code I have seen come from other pages using this method, incase it can help determine how to do this.. ----------------------------------------------------------------------------------------------------------- Original website: [login to view URL] [phpBB Debug] PHP Warning: in file /var/www/html/resources/functions/[login to view URL] on ---------------------------------------------------------------------------------------------------------- <form action="[login to view URL]" id="upload" method="POST"> <input name="crewlink" value="[login to view URL]" type="hidden"> <input name="imagelink" value="[login to view URL]" type="hidden"> <input name="crewname" value="MC Recruitment PS4" type="hidden"> <br><br> <b>Upload Agreement</b><br> <font size="-2">By uploading your image and using GTAEmblem services, you agree that your emblem complies with both our <a href="[login to view URL]">Terms of Service</a> and Social Club regulations. Failure to follow these policies may result in loss of service and/or resets without refund. Please also ensure that all artwork is copyright-free to avoid emblem removal. Uploading emblems containing pornographic content, nudity, or content that otherwise violates the our <a href="[login to view URL]">Terms of Service</a> / Social Club emblem policy will result in swift action. All emblems are logged and tracked both by staff and our internal system. Do not continue with this upload unless you have verified the content as appropriate for Social Club.<br><br></font> <input class="submitBtn" value="I Accept - Upload Emblem" type="submit"><br><br> <div style="width: 450px;"> <b>You have disabled emblem showcasing. Your emblem will not be published to the GTAEmblem Showcase.</b><br>[<a href="//[login to view URL]">Change Settings</a>] </div><br> </form>