php json_encode big array

Question

I am trying to use json_encode on a big array, and the result returns nothing (yes, I checked that it is utf-8). When I started to investigate this issue I found that the problem arise when a string becomes bigger than 65536.

So when my array is of size 1245, its string from json_encode has length of string(65493), but when I increase array by just one, the string becomes longer than 65536, json_encode fails to output any result.

I thought that the problem is because of memory limit, but when I checked my php.ini I see that it is -1.

Any idea what can be a problem?

Basically I am doing something like this:

$arr = array();
for($i =0; $i<9000; $i++){
    $arr[] = array(
        'name'  => 'test',
        'str'   => md5($i)
    );
}
echo '<pre>'.json_encode($arr).'</pre>';

It does not print the string but it is actually there? Now that's even weirder. :P — Fabrício Matté
– Fabrício Matté, Commented Aug 27, 2013 at 0:02
please take a look at this stackoverflow.com/a/6194563/562036 according to the answer provided there doesn't seem to be a limit to json_encode(), however this number 65536 seemed to the the string limit in java how did you get that? — Jianhong
– Jianhong, Commented Aug 27, 2013 at 1:49
Do you try php.net/manual/pt_BR/function.json-last-error.php ? — Cloudson
– Cloudson, Commented Aug 27, 2013 at 3:52

Giel Berkers · Accepted Answer · 2016-05-12 09:57:38Z

I had the same problem and the array was so big that increasing the memory limit didn't solve my problem. Had to write my own jsonEncode()-method to overcome this:

/**
 * Alternative to json_encode() to handle big arrays
 * Regular json_encode would return NULL due to memory issues.
 * @param $arr
 * @return string
 */
private function jsonEncode($arr) {
    $str = '{';
    $count = count($arr);
    $current = 0;

    foreach ($arr as $key => $value) {
        $str .= sprintf('"%s":', $this->sanitizeForJSON($key));

        if (is_array($value)) {
            $str .= '[';
            foreach ($value as &$val) {
                $val = $this->sanitizeForJSON($val);
            }
            $str .= '"' . implode('","', $value) . '"';
            $str .= ']';
        } else {
            $str .= sprintf('"%s"', $this->sanitizeForJSON($value));
        }

        $current ++;
        if ($current < $count) {
            $str .= ',';
        }
    }

    $str.= '}';

    return $str;
}

/**
 * @param string $str
 * @return string
 */
private function sanitizeForJSON($str)
{
    // Strip all slashes:
    $str = stripslashes($str);

    // Only escape backslashes:
    $str = str_replace('"', '\"', $str);

    return $str;
}

user4157124 · Accepted Answer · 2025-06-15 18:59:31Z

1

There is nothing wrong with json_encode function. It works correctly for every output. There is no limitation there except of your memory and how much of it are you giving to your script.

The problem was with browser's implementation of <pre> tag. If you provide too big string to this tag it does not print anything. So the way out is to output answer without <pre> tag

edited Jun 15 at 18:59

user4157124

3,00821 gold badges33 silver badges48 bronze badges

answered Oct 3, 2013 at 10:47

Salvador Dali

224k151 gold badges726 silver badges766 bronze badges

Comments

CHATHURA · Accepted Answer · 2013-10-03 10:15:46Z

0

Please try this,

$arr = array();
for($i =0; $i<3000; $i++){
$arr[] = array(
    'name'  => 'test',
    'str'   => md5($i)
);
}
$contentArr = str_split(json_encode($arr), 65536);
foreach ($contentArr as $part) {
    echo $part;
}

answered Oct 3, 2013 at 10:15

CHATHURA

1067 bronze badges

1 Comment

Wow Over a year ago

This will not work. The array is too big for the json_encode. You are trying to spit it when it already crashed

Hix.botay · Accepted Answer · 2019-01-20 15:45:08Z

0

It also occur if the array exceed memory limit, you can try change memory_limit in php.ini like

memory_limit=256M

answered Jan 20, 2019 at 15:45

Hix.botay

4336 silver badges11 bronze badges

Comments

mdehghani · Accepted Answer · 2019-07-02 09:24:46Z

0

in my case I found out that the array (derived from my database) contains strings including special characters so I made sure to convert them to utf-8 before using json_encode() function. more on that: explained here

answered Jul 2, 2019 at 9:24

mdehghani

5611 gold badge7 silver badges26 bronze badges

Collectives™ on Stack Overflow

php json_encode big array

5 Answers 5

Comments

Comments

1 Comment

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related