PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Introducing Regular Expressions
125
matches "#at". If you want to limit this to a character between a and z, you can specify
it as follows:
[a-z]at
Anything enclosed in the square brackets ([ and ]) is a character class—a set of characters
to which a matched character must belong. Note that the expression in the square
brackets matches only a single character.
You can list a set; for example,
[aeiou]
means any vowel.
You can also describe a range, as you just did using the special hyphen character, or a
set of ranges, as follows:
[a-zA-Z]
This set of ranges stands for any alphabetic character in upper- or lowercase.
You can also use sets to specify that a character cannot be a member of a set. For
example,
[^a-z]
matches any character that is not between a and z.The caret symbol (^) means not when
it is placed inside the square brackets. It has another meaning when used outside square
brackets, which we look at shortly.
In addition to listing out sets and ranges, you can use a number of predefined character
classes in a regular expression.These classes are shown in Table 4.3.
Table 4.3
Class
Character Classes for Use in POSIX-Style Regular Expressions
Matches
[[:alnum:]]
[[:alpha:]]
[[:lower:]]
[[:upper:]]
[[:digit:]]
[[:xdigit:]]
[[:punct:]]
[[:blank:]]
[[:space:]]
[[:cntrl:]]
[[:print:]]
[[:graph:]]
Alphanumeric characters
Alphabetic characters
Lowercase letters
Uppercase letters
Decimal digits
Hexadecimal digits
Punctuation
Tabs and spaces
Whitespace characters
Control characters
All printable characters
All printable characters except for space