What is the functionality of the function htmlentities?

Question

which software (html/css/js..etc etc) is required to create website like www.livebooks.com or Photoshelter.com (DIY: do it yourself).
for Frontend and backend both??

Answer 1

htmlentities will convert all applicable characters to HTML entities.

string htmlentities ( string string [, int quote_style [,
string charset]] ) 

Answer 2

htmlentities Convert all applicable characters to HTML entities This function is identical to htmlspecialchars() in all ways, except with htmlentities(), all characters which have HTML character entity equivalents are translated into these entities.