PHP regular expression import syntax

Test php regular expression here:
http://www.phpliveregex.com/
Important syntax:
  \a    control characters bell
    \b    backspace
    \f    form feed
    \n    line feed
    \r    carriage return
    \t    horizontal tab
    \v    vertical tab
special character: \. \{ \}

\s	Any whitespace character
\S	Any non-whitespace character
\d	Any digit
\D	Any non-digit
\w	Any word character (letter, number, underscore)
\W	Any non-word charact

^	Start of line
$	End of line
\A	Start of string
\z	End of string

.  Matches any single character
Examples:

• .at matches any three-character string ending with "at", including "hat", "cat", and "bat".
• [hc]at matches "hat" and "cat".
• [^b]at matches all strings matched by .at except "bat".
• [^hc]at matches all strings matched by .at other than "hat" and "cat".
• ^[hc]at matches "hat" and "cat", but only at the beginning of the string or line.
• [hc]at$ matches "hat" and "cat", but only at the end of the string or line.
• \[.\] matches any single character surrounded by "[" and "]" since the brackets are escaped, for example: "[a]" and "[b]".