I figured out the issue that I was having and to fix it, I used JSZip to convert this to data:application/zip;base64. This encoded it properly and on the php endpoint, I decoded this into a tmp file, used inkscape to convert and returned the base64 encoded string of the newly created png. The issue was not using file_get_contents so the string that was being encoded didn't exist. I hope this helps someone else out there with a similar situation.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…