Pretty much all of the frameworks have a pretty good security. Companies geared in ecommerce development based on Magento will require you to know Zend. Magento is based on the Zend Framework. However, there is a pretty steep learning curve in Zend. You will have to know the basics of MVC design pattern first and then move on to Zend, else prepare to pay a high price for the course being offered by Zend.
There are some companies doing ecommerce development based on CodeIgniter, Laravel and Kohana. Most corporate and business websites are built on CI with foundation or bootstrap. There are some downside to using CI. CI is no longer being maintain by its creator. Meaning, that from that day Ellis Lab ceased their support, you are on your own. Using CI to this date requires you to be able to write your own module. For example, the password module is not as effecient as the latest PHP password hash function found in PHP 5.5.x or higher. You will need to know how to create a modules and helpers for CI so that you can utilize this.
Regardless on which one you learned and mastered, employer will always look for proficiency in OOP, MVC design patterns, and the knowledge and experience in creating an application in either one or two of these frameworks CI, Kohana, Laravel, Zend, or Symfony 2.
If you are crazy like me, learn all of them and you wouldn't be asking this type of question ever again.