$re = '/\{code\}(.*?)\{code\}/ms';
$str = '{code}
UPDATE tenants SET end_user_uuid = \'32392464c8a19a15dd8dc982ae3d574b\' WHERE end_user_uuid = \'9e194bfeace6c2d17cc71cc15e84f93a\' AND instance_id = \'265358\' AND domain = \'automobieljansen\';
{code}';
$subst = "<pre>$1</pre>";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php