index_U

U

U format, date function, 281

ucfirst() function, 305

ucwords() function, 305

underscore character (_), 34, 252

uniqid() function, 295–296

unique identifiers in databases, importance of, 77–78

Unix

installing and configuring Apache on, 3–7

installing PHP on, 11–13

unlink() function, 288

unset() function, 305–306

untar command, 11

unzip command, 11

UPDATE command, 88, 186

URLs, redirecting users to, 57–60

user and group files

Basic HTTP authentication, 137–139

database-driven authentication, 142–144

validation, 144–149

user authentication. See authentication

users

preferences, managing, 156–161

validation, 144–149

usleep() function, 295