Solution to PHP Fatal error: Uncaught Error: Call to undefined function json_encode()

If you encounter the error message PHP Fatal error: Uncaught Error: Call to undefined function json_encode() when writing a project in PHP, don’t panic. This is because your PHP version does not support the json_encode() function. The json_encode() function is a very commonly used function in PHP, used to convert arrays or objects into JSON strings. So how to solve this error? Let’s take a look at the solution below.

1. Check PHP version

First you need to check your current PHP version. If your PHP version is lower than 5.2.0, then you need to upgrade PHP to 5.2.0 or above. The json_encode() function was introduced starting from version 5.2.0.

You can enter php -v in the terminal or command line to view the current PHP version.

2. Install JSON extension

If your PHP version is higher than 5.2.0 and this error message still appears, you need to install the JSON extension.

In Windows environment, you can find the php_json.dll file in the ext folder of the PHP installation directory and copy it to the PHP directory. Then add extension=php_json.dll to the php.ini file to enable the JSON extension.

In a Linux environment, you can run the following command to install the JSON extension:

sudo apt-get install php7.0-json

sudo service php7.0-fpm restart

The above commands are for reference only and should be adjusted according to your PHP version.

3. Enable json extension

If you installed the JSON extension and still get this error, it may be because the JSON extension is not enabled. You can enable the JSON extension by adding the following content to the php.ini file:

extension=json.so

or manually enable the JSON extension in the code:

if (!function_exists ('json_decode')) {

function json_decode($content, $assoc = false) {

    require_once 'Services/JSON.php';

    if ($assoc) {

        $json = new Services_JSON(SERVICES_JSON_LOOSE_TYPE);

    } else {

        $json = new Services_JSON;

    }

    return $json->decode($content);

}

}

if (!function_exists('json_encode')) {

function json_encode($content) {

    require_once 'Services/JSON.php';

    $json = new Services_JSON;

    return $json->encode($content);

}

}

In this method , we manually defined the json_encode() and json_decode() functions, which can ensure that our code can be executed correctly under any PHP version.

Summary

Among the above three methods, the second method is the most recommended, which is to install the JSON extension. This not only solves the problem of the json_encode() function, but also allows you to use more JSON-related functions and tools. At the same time, in order to ensure that your project can run normally in various environments, we also recommend that you add the above content to your code to ensure that it can run in environments without JSON extensions.

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