Php Regular Expressions

Date Added: 14/01/2015

Regular Expression	Will match...
foo	The string "foo"
^foo	"foo" at the start of a string
foo$	"foo" at the end of a string
^foo$	"foo" when it is alone on a string
[abc]	a, b, or c
[a-z]	Any lowercase letter
[^A-Z]	Any character that is not a uppercase letter
(gif\|jpg)	Matches either "gif" or "jpeg"
[a-z]+	One or more lowercase letters
[0-9\.\-]	?ny number, dot, or minus sign
^[a-zA-Z0-9_]{1,}$	Any word of at least one letter, number or _
([wx])([yz])	wy, wz, xy, or xz
[^A-Za-z0-9]	Any symbol (not a number or a letter)
([A-Z]{3}\|[0-9]{4})	Matches three letters or four numbers

Regular Expressions Reference Sheet
Character	Definition	Example
^	The pattern has to appear at the beginning of a string.	^cat matches any string that begins with cat
$	The pattern has to appear at the end of a string.	cat$ matches any string that ends with cat
.	Matches any character.	cat. matches catT and cat2 but notcatty
[]	Bracket expression. Matches one of any characters enclosed.	gr[ae]y matches gray or grey
[^]	Negates a bracket expression. Matches one of any characters EXCEPT those enclosed.	1[^02] matches 13 but not 10 or12
[-]	Range. Matches any characters within the range.	[1-9] matches any single digit EXCEPT 0
?	Preceeding item must match one or zero times.	colou?r matches color or colour but not colouur
+	Preceeding item must match one or more times.	be+ matches be or bee but not b
*	Preceeding item must match zero or more times.	be* matches b or be orbeeeeeeeeee
()	Parentheses. Creates a substring or item that metacharacters can be applied to	a(bee)?t matches at or abeet but not abet
{n}	Bound. Specifies exact number of times for the preceeding item to match.	[0-9]{3} matches any three digits
{n,}	Bound. Specifies minimum number of times for the preceeding item to match.	[0-9]{3,} matches any three or more digits
{n,m}	Bound. Specifies minimum and maximum number of times for the preceeding item to match.	[0-9]{3,5} matches any three, four, or five digits
\|	Alternation. One of the alternatives has to match.	July (first\|1st\|1) will match July 1stbut not July 2
POSIX Character Classes
Character	Definition	Example
[:alnum:]	alphanumeric character	[[:alnum:]]{3} matches any three letters or numbers, like 7Ds
[:alpha:]	alphabetic character, any case	[[:alpha:]]{5} matches five alphabetic characters, any case, like aBcDe
[:blank:]	space and tab	[[:blank:]]{3,5} matches any three, four, or five spaces and tabs
[:digit:]	digits	[[:digit:]]{3,5} matches any three, four, or five digits, like 3, 05, 489
[:lower:]	lowercase alphabetics	[[:lower:]] matches a but not A
[:punct:]	punctuation characters	[[:punct:]] matches ! or . or , but not a or 3
[:space:]	all whitespace characters, including newline and carriage return	[[:space:]] matches any space, tab, newline, or carriage return
[:upper:]	uppercase alphabetics	[[:upper:]] matches A but not a
Perl-Style Metacharacters
Character	Definition	Example
//	Default delimiters for pattern	/colou?r/ matches color or colour
i	Append to pattern to specify a case insensitive match	/colou?r/i matches COLOR orColour
\b	A word boundary, the spot between word (\w)and non-word (\W) characters	/\bfred\b/i matches Fred but notAlfred or Frederick
\B	A non-word boundary	/fred\B/i matches Frederick but notFred
\d	A single digit character	/a\db/i matches a2b but not acb
\D	A single non-digit character	/a\Db/i matches aCb but not a2b
\n	The newline character. (ASCII 10)	/\n/ matches a newline
\r	The carriage return character. (ASCII 13)	/\r/ matches a carriage return
\s	A single whitespace character	/a\sb/ matches a b but not ab
\S	A single non-whitespace character	/a\Sb/ matches a2b but not a b
\t	The tab character. (ASCII 9)	/\t/ matches a tab.
\w	A single word character - alphanumeric and underscore	/\w/ matches 1 or _ but not ?
\W	A single non-word character	/a\Wb/i matches a!b but not a2b