PHP TUTORIALS - PHP Regular Expression

PHP Regular Expression

POSIX Regular Expressions:

Expression	Description
[0-9]	It matches any decimal digit from 0 through 9.
[a-z]	It matches any character from lowercase a through lowercase z.
[A-Z]	It matches any character from uppercase A through uppercase Z.
[a-Z]	It matches any character from lowercase a through uppercase Z.

Expression	Description
p+	It matches any string containing at least one p.
p*	It matches any string containing zero or more p's.
p?	It matches any string containing zero or more p's. This is just an alternative way to use p*.
p{N}	It matches any string containing a sequence of N p's
p{2,3}	It matches any string containing a sequence of two or three p's.
p{2, }	It matches any string containing a sequence of at least two p's.
p$	It matches any string with p at the end of it.
^p	It matches any string with p at the beginning of it.

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Expression	Description
[^a-zA-Z]	It matches any string not containing any of the characters ranging from a through z and A through Z.
p.p	It matches any string containing p, followed by any character, in turn followed by another p.
^.{2}$	It matches any string containing exactly two characters.
<b>(.*)</b>	It matches any string enclosed within <b> and </b>.
p(hp)*	It matches any string containing a p followed by zero or more instances of the sequence hp.

Expression	Description
[[:alpha:]]	It matches any string containing alphabetic characters aA through zZ.
[[:digit:]]	It matches any string containing numerical digits 0 through 9.
[[:alnum:]]	It matches any string containing alphanumeric characters aA through zZ and 0 through 9.
[[:space:]]	It matches any string containing a space.

PERL Style Regular Expressions:


Character		Description
.              a single character
\s             a whitespace character (space, tab, newline)
\S             non-whitespace character
\d             a digit (0-9)
\D             a non-digit
\w             a word character (a-z, A-Z, 0-9, _)
\W             a non-word character
[aeiou]        matches a single character in the given set
[^aeiou]       matches a single character outside the given set
(foo|bar|baz)  matches any of the alternatives specified


Modifier	Description
i 	Makes the match case insensitive
m 	Specifies that if the string has newline or carriage
	return characters, the ^ and $ operators will now
	match against a newline boundary, instead of a
	string boundary
o 	Evaluates the expression only once
s 	Allows use of . to match a newline character
x 	Allows you to use white space in the expression for clarity
g 	Globally finds all matches
cg 	Allows a search to continue even after a global match fails