php json_encode() automatically added slashes before slashes

I am storing my data in the form of json to the database. User can input with quotes, so i am manually adding slashes before the quotes. So my data becomes like this

array:8 [▼
  "buttonText" => "Large Button"
  "campName" => "Large\'s Button Test"
  "buttonSize" => "1"
]

But when i am converting it into json, the json_encode() function automatically added one more slash before my slash as

"{"buttonText":"Large Button","campName":"Large\\'s Button Test","buttonSize":"1"}"

Why the extra slash will be added, is there any option to prevent that

via Chebli Mohamed