What References Are References in PHP are a means to access the
same variable content by different names. They are not like C
pointers; for instance, you cannot perform pointer arithmetic
using them, they are not actual memory addresses, and so on. See
What References Are Not for more information. Instead, they are
symbol table aliases. Note that in PHP, variable name and
variable content are different, so the same content can have
different names. The closest analogy is with Unix filenames and
files - variable names are directory entries, while variable
content is the file itself. References can be likened to
hardlinking in Unix filesystem.