from my understanding, the main difference between the two is that when you use single quotes it is generally faster and it is also the easiest way to define a string. Also, all of the escape sequences will be output as they are written in the code, instead of having any special meaning. When you use double quotes in PHP, the code will be forced to evaluate the whole entire string. By using double quotes it is possible to include variables in the string. Special sequences like Escape will be interpretted corectly when you use double quotes.