I have this JSON object stored on a plain text file:

{
    "MySQL": {
        "Server": "(server)",
        "Username": "(user)",
        "Password": "(pwd)",
        "DatabaseName": "(dbname)"
    },
    "Ftp": {
        "Server": "(server)",
        "Username": "(user)",
        "Password": "(pwd)",
        "RootFolder": "(rf)"
    },
    "BasePath": "../../bin/",
    "NotesAppPath": "notas",
    "SearchAppPath": "buscar",
    "BaseUrl": "http:\/\/montemaiztusitio.com.ar",
    "InitialExtensions": [
        "nem.mysqlhandler",
        "nem.string",
        "nem.colour",
        "nem.filesystem",
        "nem.rss",
        "nem.date",
        "nem.template",
        "nem.media",
        "nem.measuring",
        "nem.weather",
        "nem.currency"
    ],
    "MediaPath": "media",
    "MediaGalleriesTable": "journal_media_galleries",
    "MediaTable": "journal_media",
    "Journal": {
        "AllowedAdFileFormats": [
            "flv:1",
            "jpg:2",
            "gif:3",
            "png:4",
            "swf:5"
        ],
        "AdColumnId": "3",
        "RSSLinkFormat": "%DOMAIN%\/notas\/%YEAR%-%MONTH%-%DAY%\/%TITLE%/",
        "FrontendLayout": "Flat",
        "AdPath": "ad",
        "SiteTitle": "Monte Maíz: Tu Sitio",
        "GlobalSiteDescription": "Periódico local de Monte Maíz.",
        "MoreInfoAt": "Más información aquí, en el Periódico local de Monte Maíz.",
        "TemplatePath": "templates",
        "WeatherSource": "accuweather:SAM|AR|AR005|MONTE MAIZ",
        "WeatherMeasureType": "1",
        "CurrencySource": "cotizacion-monedas:Dolar|Euro|Real",
        "TimesSingular": "vez",
        "TimesPlural": "veces"
    }
}

When I try to decode it with json_decode(), it returns NULL. Why? The file is readable (I tried echoing file_get_contents() and it worked ok).

I've tested JSON against http://jsonlint.com/ and it's perfectly valid.

What's wrong here?

Solution

Looking for answers on Google, I got back to SO: json_decode returns NULL after webservice call. My JSON file had the UTF BOM sequence (some binary chars that shouldn't be there), thus, breaking the JSON structure. Went to Hex Editor, erased the bytes. Everything's back to normal. Why has this happened? Because I edited the file using Microsoft Windows' Notepad. Terrible idea!

It could be the encoding of the special characters. You could ask json_last_error() to get definite information.

Update: The issue is solved, look at the "Solution" paragraph in the question.

If you check the the request in chrome you will see that the JSON is text, so there has been blank code added to the JSON.

You can clear it by using

$k=preg_replace('/\s+/', '',$k);

Then you can use:

json_decode($k)

print_r will then show the array.

$k=preg_replace('/\s+/', '',$k); 

did it for me. And yes, testing on Chrome. Thx to user2254008

As stated by Jürgen Math using the preg_replace method listed by user2254008 fixed it for me as well.

This is not limited to Chrome, it appears to be a character set conversion issue (at least in my case, Unicode -> UTF8) This fixed all the issues i was having.

As a future node, the JSON Object i was decoding came from Python's json.dumps function. This in turn caused some other unsanitary data to make it across though it was easily dealt with.

<?php 
$json_url = "http://api.testmagazine.com/test.php?type=menu";
$json = file_get_contents($json_url);
$json=str_replace('},

]',"}

]",$json);
$data = json_decode($json);

echo "<pre>";
print_r($data);
echo "</pre>";
?>

Just thought I'd add this, as I ran into this issue today. If there is any string padding surrounding your JSON string, json_decode will return NULL.

If you're pulling the JSON from a source other than a PHP variable, it would be wise to "trim" it first:

$jsonData = trim($jsonData);

I had the same problem and I solved it simply by replacing the quote character before decode.

$json = str_replace('"', '"', $json);
$object = json_decode($json);

My JSON value was generated by JSON.stringify function.

This worked for me

json_decode( preg_replace('/[\x00-\x1F\x80-\xFF]/', '', $json_string), true );

If you are getting json from database, put

mysqli_set_charset($con, "utf8");

after defining connection link $con

Just save some one time. I spent 3 hours to find out that it was just html encoding problem. Try this

if(get_magic_quotes_gpc()){
   $param = stripslashes($row['your column name']);
}else{
  $param = $row['your column name'];
}

$param = json_decode(html_entity_decode($param),true);
$json_errors = array(
JSON_ERROR_NONE => 'No error has occurred',
JSON_ERROR_DEPTH => 'The maximum stack depth has been exceeded',
JSON_ERROR_CTRL_CHAR => 'Control character error, possibly incorrectly encoded',
JSON_ERROR_SYNTAX => 'Syntax error',
);
echo 'Last error : ', $json_errors[json_last_error()], PHP_EOL, PHP_EOL;
print_r($param);

You could try with it.

json_decode(stripslashes($_POST['data']))

Maybe some hidden characters are messing with your json, try this:

$json = utf8_encode($yourString);
$data = json_decode($json);

I've solved this issue by printing the JSON, and then checking the page source (CTRL/CMD + U):

print_r(file_get_contents($url));

Turned out there was a trailing <pre> tag.

this help you to understand what is the type of error

<?php
// A valid json string
$json[] = '{"Organization": "PHP Documentation Team"}';

// An invalid json string which will cause an syntax 
// error, in this case we used ' instead of " for quotation
$json[] = "{'Organization': 'PHP Documentation Team'}";


foreach ($json as $string) {
    echo 'Decoding: ' . $string;
    json_decode($string);

    switch (json_last_error()) {
        case JSON_ERROR_NONE:
            echo ' - No errors';
        break;
        case JSON_ERROR_DEPTH:
            echo ' - Maximum stack depth exceeded';
        break;
        case JSON_ERROR_STATE_MISMATCH:
            echo ' - Underflow or the modes mismatch';
        break;
        case JSON_ERROR_CTRL_CHAR:
            echo ' - Unexpected control character found';
        break;
        case JSON_ERROR_SYNTAX:
            echo ' - Syntax error, malformed JSON';
        break;
        case JSON_ERROR_UTF8:
            echo ' - Malformed UTF-8 characters, possibly incorrectly encoded';
        break;
        default:
            echo ' - Unknown error';
        break;
    }

    echo PHP_EOL;
}
?>

you should ensure these points

1. your json string dont have any unknowns characters

2. json string can view from online json viewer (you can search on google as online viewer or parser for json) it should view without any error

3. your string dont have html entities it should be plain text/string

for explanation of point 3

$html_product_sizes_json=htmlentities($html);
    $ProductSizesArr = json_decode($html_product_sizes_json,true);

to (remove htmlentities() function )

$html_product_sizes_json=$html;
    $ProductSizesArr = json_decode($html_product_sizes_json,true);

Here you can find little JSON wrapper with corrective actions that addresses BOM and non-ASCI issue: https://stackoverflow.com/a/43694325/2254935

For my case, it's because of the single quotes in the JSON string.

JSON format only accepts double-quotes for keys and string values.

Example:

$jsonString = '{\'hello\': \'PHP\'}'; // valid value should be '{"hello": "PHP"}'
$json = json_decode($jsonString);
print $json; // null

I got this confusing because of Javascript syntax. In Javascript, of course, we can do like this:

let json = {
    hello: 'PHP' // no quote for key, single quote for string value
}

// OR:
json = {
    'hello': 'PHP' // single quote for key and value
}

but later when convert those objects to JSON string:

JSON.stringify(json); // "{"hello":"PHP"}"