Magento – Fix Deprecated mysql_connect() Error: Use mysqli or PDO Instead

cleanPasswordsValidationData()is not a default method available in Magento. So I guess you have some customizations which are carried out in AccountController.php or there may be a rewrite for this very same class.

During customer registration, magento will execute createPostAction() method which is present in app/code/core/Mage/Customer/controllers/AccountController.php. If you inspect this method, you can't find a method with name cleanPasswordsValidationData() which is called up on a customer instance.

Even-though you comment it out the line which holds cleanPasswordsValidationData(), that line of code is intended to use some validation on posted data which is important in case of customer registration process. So instead of commenting it out, you need to dig from there and make the validation correct.

May be this customization is done during development of the site. Contact the developer if you are not a developer. That's the only possibility to resolve this issue.

The e modifier is short for eval. It performs a back reference substitution, then executes the replacement string as PHP, then performs the substitution using the returned value.

For example:

$pattern     = '/(.*)/e';
$replacement = 'strtoupper("$0");';
$input       = 'hello';
echo preg_replace($pattern, $replacement, $input);

Can be translated into:

$pattern     = '/(.*)/';
$input       = 'hello';
echo preg_replace_callback($pattern, function ($matches) {
    return strtoupper($matches[0]);
}, $input);

Without knowing what's returned by @file_get_contents($stylesheet) it's a little difficult to give accurate advice. The most obvious answer is the following, however be warned, this is pretty much as insecure as the e modifier (which is why it's deprecated):

echo preg_replace_callback('/\$([\w]+)/', function ($matches) {
    return eval($matches[0]);
}, $input);