json_encode returns null on valid JSON string

Question

I'm using PHP's json_decode function to parse a JSON string created by JavaScript's JSON.stringify;

JSON appears to be valid:

JSON String:

"{"m_user_name":"test","m_user_phone":" 60 12-384 7961","m_user_city":"Kuala Lumpur","m_user_linkedin ":"example@gmail.com","m_user_g_plus":"example@gmail.com"}"

JSON final error message: "Syntax error"

Okay, if I paste the string directly into json_decode it works. I'm sending a string via ajax via a form_data object and then trying to decode the post variable.

The following is the code for the ajax request:

$.ajax({
  type: "POST",
  url: ajaxurl,
  data: formdata,
  cache: false,
  contentType: false,
  processData: false,

  beforeSend: function () {
    toggle_loading_spinner();
  },
  success: function (data) {
    console.log(data);

    toggle_loading_spinner();
  },
});

I tried using preg_replace('/[x00-x1Fx80-xFF]/', '', $JSON_STRING) to remove the unwanted symbols, but I got the same error.

Answer 1

json_decode() function only works with strings encoded in UTF-8. The input may be in a different encoding. After removing the unwanted characters, try converting the encoding to UTF-8. Here are references on how to do the conversion:

https://www.php.net/manual/en/function.mb-convert-encoding.php