json_decode() returning error “Notice: Trying to get property of non-object”

问题

I am trying to write a script that gets a JSON file from a remote location (in this case being twitch.tv) using cURL (don't think that part is too relevant, though I better mention it anyway). For example purposes, lets say the JSON object it returns looks something like this after being stored in a variable:

$json_object = {"_links":{"self":"https://api.twitch.tv/kraken/streams/gmansoliver","channel":"https://api.twitch.tv/kraken/channels/gmansoliver"},"stream":null}

I access the "stream" property, I have tried the follow code:

<?php
    $json_object = {"_links":{"self":"https://api.twitch.tv/kraken/streams/gmansoliver","channel":"https://api.twitch.tv/kraken/channels/gmansoliver"},"stream":null}

    $json_decoded = json_decode($json_object, true);
    echo $json_decoded->stream;
?>

When I try this, I get the error "Notice: Trying to get property of non-object in D:\Servers\IIS\Sites\mysite\getstream.php on line 48".

Am I using json_decode() wrong, or is there something wrong with the JSON object I am being sent from twitch?

Edit:

I now have the JSON object:

{"access_token": "qwerty1235","refresh_token": "asdfghjkl=","scope": ["user_read"]}

If I try to decode it using json_decode() I get the following error: Object of class stdClass could not be converted to string. Any advice?

Thanks in advance for any help

回答1:

You're decoding the JSON into an array. json_decode($json_object, true); Will return an array

array (size=2)
  '_links' => 
    array (size=2)
      'self' => string 'https://api.twitch.tv/kraken/streams/gmansoliver' (length=48)
      'channel' => string 'https://api.twitch.tv/kraken/channels/gmansoliver' (length=49)
  'stream' => null

If you remove the second parameter and run it as json_decode($json_object)

object(stdClass)[1]
  public '_links' => 
    object(stdClass)[2]
      public 'self' => string 'https://api.twitch.tv/kraken/streams/gmansoliver' (length=48)
      public 'channel' => string 'https://api.twitch.tv/kraken/channels/gmansoliver' (length=49)
  public 'stream' => null

See the documentation, When TRUE, returned objects will be converted into associative arrays.

回答2:

You have set the second parameter ($assoc) of json_decode() to true, which means it's going to return an associative array instead of an object. You then tried to reference the object style. If you are setting the second parameter to true, you need to use the associative array style to access the stream content. It would be:

$json_decoded['stream']

If you set the $assoc parameter to false (or do not specify the parameter) then you can reference it as an object:

$json_decoded->stream

If you do var_dump on the $json_decoded variable you will see what it looks like. This is a good way to see what you are working with.

来源：https://stackoverflow.com/questions/25195010/json-decode-returning-error-notice-trying-to-get-property-of-non-object

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