You may have read about the recent tragic electrocution of a young girl while she apparently was handling a phone while in her bathtub. Here is an article by a noted RV electrician on the safety aspects of chargers and phones. I encourage you to read it. More articles from this gentleman can be read here.
The following statement from the article really caught my attention: "all phone chargers will energize the metal of your phone with around ½ of the line voltage, albeit at an extremely low current."
Frequently chargers for your electric device -- whether it be a phone, tablet, or computer -- can be purchased at flea markets at a very cheap price. This is especially true for Apple devices. My recommendation is don't ever buy these imitation copies. They probably are cheaply-built and dangerous. Pay a bit more and buy these from Apple or a reputable dealer.