[PHP] ERRORE: SyntaxError: Unexpected token N in JSON at position 1

[nofcfro]

Salve,
quando carico le immagini ottengono questo errore:

SyntaxError: Unexpected token N in JSON at position 1

ho letto questa guida ma non riesco a venirne a capo:
https://teamtreehouse.com/community/syntaxerror-unexpected-token-n-in-json-at-position-0-please-help