Fatal error: Call to undefined function mb_convert_encoding() in /home/abcdef/public_html/folder_name/lib/Pelago/Emogrifier.php on line 556 - magento-1.9

Question

Fatal error: Call to undefined function mb_convert_encoding() in
/home/abcdef/public_html/folder_name/lib/Pelago/Emogrifier.php on line
556
solve this error in magento code.
this is the code , at return line its showing error.
private function getUnifiedHtml() {
if (!empty($this->unprocessableHtmlTags)) { $unprocessableHtmlTags = implode('|', $this->unprocessableHtmlTags); $bodyWithoutUnprocessableTags = preg_replace('/<\\/?(' . $unprocessableHtmlTags . ')[^>]*>/i', '', $this->html); } else { $bodyWithoutUnprocessableTags = $this->html; }
return mb_convert_encoding($bodyWithoutUnprocessableTags, 'HTML-ENTITIES', self::ENCODING);
}

Answer 1

It looks like you are missing a PHP extension mbstring.
Install it and the error will be rectified.
Ubuntu/Debian
sudo apt-get install php-mbstring
In case you are using PHP 7.x.
sudo apt-get install php7.0-mbstring
For Centos
sudo yum install php-mbstring

Answer 2

I'm updating this thread with the instructions for GoDaddy hosted servers, as I went through a painful day trying to get this resolved. The mbstring extension is used by Magento (I needed it for 1.9) and without it installed, the checkout process will fail, with the shopping cart failing to take the user to the 'Thanks for your order screen' (although the order is sometimes created on the back-end successfully). It was also creating an issue when hitting the 'Send Email' button on the Admin panel on an Order, producing a 500 error.
In my log files, I was seeing the following error:
PHP Fatal error: Call to undefined function mb_convert_encoding() in
/home/yoursite/public_html/lib/Pelago/Emogrifier.php on line 556
Searching for this error gave results that suggested I needed to enable the mbstring extension on the server, but with a GoDaddy hosted virtual server, I ran into a wall of frustration with the package not being found via the php install search, and their tech support unable to assist. Here are the instructions for the current WHM panel (Jan 2019):
Login to your server WHM as root.
Search EasyApache or go to the Software menu on the left and select 'EasyApache 4'.
You will see a list of profiles and at the top of the list, 'Currently Installed Packages'. Select the 'Customize' button.
Select the 'PHP Extensions' link or keep hitting 'Next' until you reach the page.
In the search box, type 'string', you will see 'php56-php-mbstring' and 'php70-php-mbstring'; move the grey slider on the right to install each.
Continue to the 'Review' tab. Here you can simply hit 'Provision' to install the extension. You can also save these options as a custom profile if you'd like.
After the build has completed, the extension should be available on all your domains.
Hopefully this will save someone some time trying to figure this out!