Special symbols in PHP's regular expressions _ regular expressions

Characters
Meaning: For a character, it is usually indicated by literal meaning that the character followed by a special character is not interpreted.
For example:/b/matches the character ' B ', which becomes a special character by adding a backslash before B, i.e./b/, which means
Match the dividing line of a word.
Or:
For a few characters, usually the description is special, indicating that the character immediately followed is not special, but should be interpreted literally.
For example: * is a special character that matches any character (including 0 characters), for example:/a*/means matching 0 or more aces. To match the literal *, precede a with a backslash; For example:/a*/matches a ' * '.

Character ^
Meaning: The character that matches must be at the front.
For example:/^a/does not match the ' a ' in ' an A ', but matches ' an A. ' The "A" in the front.

Character $
Meaning: Similar to ^, matches the last character.
For example:/t$/does not match ' t ' in ' eater ', but matches ' t ' in ' eat '.

Characters
Meaning: matches the characters of the preceding 0 or n times.
For example:/bo*/matches ' B ' in ' boooo ' or ' a bird warbled ' in ' a ghost booooed ', but does not match ' agoat g
runted any character in the ".

Character +
Meaning: Matches the character preceded by the + number 1 or n times. Equivalent to {1,}.
For example:/a+/matches ' a ' and ' Caaaaaaandy ' in ' Candy '. All ' a ' in.

Character?
Meaning: match the preceding character 0 or 1 times.
For example:/e?le?/matches ' el ' and ' angle ' in ' Angel '. ' Le ' in the.

Character.
Meaning: (decimal point) matches all individual characters except for line breaks.
For example:/.n/matches ' an ' and ' on ' in the ' nay ', an apple are on the tree, but does not match ' nay '.


Character (x)
Meaning: Matches ' X ' and records the matching value.
For example:/(foo)/Match and record "Foo bar." In the ' foo '. The matching substring can be in the result array of the element [1], ..., [n] Return
Back, or the properties of the object being RegExp, ..., returned.

Character X│y
Meaning: Match ' x ' or ' Y '.
For example:/green│red/matches ' green ' and ' Red apple ' in ' green apple '. In the ' Red '.

Character {n}
Meaning: Here The n is a positive integer. Matches the preceding n characters.
For example:/a{2}/does not match "candy," in ' a ', but matches "Caandy," in all ' a ' and ' Caaandy. ' In front of the two ' a '.

Character {n,}
Meaning: Here The n is a positive integer. Matches at least n preceding characters.
For example:/a{2,} does not match ' a ' in ' Candy ', but matches all ' a ' and ' Caaaaaaandy ' in ' Caandy '. All ' a ' in the

Character {n,m}
Meaning: Here the N and M are all positive integers. Matches at least n up to m preceding characters.
For example:/a{1,3}/does not match any character in "Cndy", but matches the front two in "a", "Candy," in "Caandy,"
"A" and "Caaaaaaandy" in front of the three ' a ', note: even if "caaaaaaandy" there are many ' a ', but only match the preceding three ' a ' that is ' AAA '.

character [XYZ]
Meaning: A list of characters that matches any one of the characters listed. You can indicate a range of characters through hyphens.
For example: [ABCD] is the same as [a-c]. They match the ' C ' in ' B ' and ' ache ' in ' brisket '.

character [^XYZ]
Meaning: A character complement, that is, it matches everything except the characters listed. You can use hyphens--to indicate a range of characters.
For example: [^ABC] and [^a-c] are equivalent, they first match the ' R ' and ' chop ' in ' brisket '. In the ' H '.

Character
Meaning: Match a space (do not confuse with B)

Character B
Meaning: Match the dividing line of a word, such as a space (not with confusion)
For example:/bnw/matches ' no ' in ' Noonday ',/wyb/matches ' possibly yesterday. ' In the ' ly '.

Character B
Meaning: A non-dividing line that matches a word
For example:/wbn/matches ' on ' in ' Noonday ',/ybw/matches ' possibly yesterday. ' In the ' ye '.

Character CX
Meaning: Here The X is a control character. Matches the control character of a string.
For example:/cm/matches the control-m in a string.

Character D
Meaning: Matches a number, equivalent to [0-9].
For example:/d/or/[0-9]/matches "B2 is the" suite number. In the ' 2 '.

Character D
Meaning: Matches any non-numeric, equivalent to [^0-9].
For example:/d/or/[^0-9]/matches "B2 is the" suite number. In the ' B '.

Character F
Meaning: matches a form character

Character N
Meaning: matches a newline character

Character R
Meaning: matches a carriage return character

Character S
Meaning: Matches a single white spaces, including spaces, tab,form feeds, line breaks, equivalent to [FNRTV].
For example:/sw*/matches "foo bar." ' Bar ' in the.

Character S
Meaning: matches a single character except white spaces, equivalent to [^ FNRTV].
For example:/s/w* matches "foo bar." In the ' foo '.

Character T
Meaning: Match a tab

Character V
Meaning: Match a head tab

Character W
Meaning: Matches all numbers and letters and underscores, equivalent to [a-za-z0-9_].
For example:/w/matches the ' a ', '. 28, ' in ' 5 ' and ' 3D ' in ' apple '. In the ' 3 '.

Character W
Meaning: Matches other characters except numbers, letters, and underscores, equivalent to [^a-za-z0-9_].
For example:/w/or/[^ $A-za-z0-9_]/match "50%." In the '% '.

Character N
Meaning: Here The n is a positive integer. Matches the value of N of the last substring of a regular expression (counting the left parenthesis).

For example:/apple (,) sorange1/match "Apple, orange, cherry, peach." In the ' Apple, Orange ', here is a more complete example.
Note: If the number in the left parenthesis is smaller than the number specified in N, then N takes a row of octal escape as a description.

Character Ooctal and Xhex
Meaning: Here the ooctal is a octal escape value, and Xhex is a hexadecimal escape value that allows ASCII code to be embedded in a regular expression

Attached: The following table is a complete list of metacharacters and its behavior in the context of regular expressions:

Character description
\
Marks the next character as a special character, or a literal character, or a back reference, or a octal escape character. For example, ' n ' matches the character ' n '. ' \ n ' matches a newline character. Sequence ' \ ' matches ' and ' \ (' Matches ' (".
^
Matches the start position of the input string. If the Multiline property of the RegExp object is set, ^ also matches the position after ' \ n ' or ' \ R '.
$
Matches the end position of the input string. If the Multiline property of the RegExp object is set, the $ also matches the position before ' \ n ' or ' \ R '.
*
Matches the preceding subexpression 0 or more times. For example, zo* can match "z" and "Zoo". * is equivalent to {0,}.
+ matches the preceding subexpression one or more times. For example, ' zo+ ' can match "Zo" and "Zoo", but cannot match "Z". + is equivalent to {1,}.
?
Match the preceding subexpression 0 times or once. For example, "Do (es)" can match "do" in "do" or "does". is equivalent to {0,1}.
N
n is a non-negative integer. Matches the determined n times. For example, ' o{2} ' cannot match ' o ' in ' Bob ', but can match two o in ' food '.
{N,}
n is a non-negative integer. Match at least n times. For example, ' o{2,} ' cannot match ' o ' in ' Bob ' but can match all o in ' Foooood '. ' O{1,} ' is equivalent to ' o+ '. ' O{0,} ' is equivalent to ' o* '.
{N,m}
M and n are nonnegative integers, of which n <= M. Matches n times at least and matches up to M times. Liu, "o{1,3}" will match the first three o in "Fooooood". ' o{0,1} ' is equivalent to ' o '. Notice that there is no space between the comma and the two number.
?
When the character is immediately following any of the other qualifiers (*, +,?, {n}, {n,}, {n,m}), the matching pattern is not greedy. Non-greedy patterns match as few strings as possible, while the default greedy pattern matches as many of the searched strings as possible. For example, for the string "oooo", ' o+? ' will match a single "O", and ' o+ ' will match all ' o '.
.
Matches any single character except "\ n". To match any character including ' \ n ', use a pattern like ' [. \ n] '.
(pattern)
Match pattern and get this match. The obtained matches can be obtained from the resulting matches collection, using the Submatches collection in VBScript, and using the {CONTENT} in JScript ... Property. To match the parentheses character, use ' \ (' or ' \ ').
(?:p Attern)
Matches pattern but does not get a matching result, which means it is a non fetch match and is not stored for later use. This is useful for combining parts of a pattern with the "or" character (|). For example, ' Industr (?: y|ies) is a more abbreviated expression than ' industry|industries '.
(? =pattern)
Forward lookup, matching the find string at the beginning of any string matching pattern. This is a non-fetch match, that is, the match does not need to be acquired for later use. For example, ' Windows (? =95|98| nt|2000) ' Can match windows in Windows 2000, but cannot match windows in Windows 3.1. It does not consume characters, that is, after a match occurs, the next matching search begins immediately after the last match, instead of starting after the character that contains the pre-check.
(?! Pattern
A negative check matches the lookup string at the beginning of any mismatched negative lookahead matches the search string at either point where a string is not matching. This is a non-fetch match, that is, the match does not need to be acquired for later use. For example, ' Windows (?! 95|98| nt|2000) ' Can match windows in Windows 3.1, but cannot match windows in Windows 2000. It does not consume characters, that is, after a match occurs, the next matching search begins immediately after the last match, instead of starting after the character that contains the pre-check.
X|y
Match x or Y. For example, ' Z|food ' can match "z" or "food". ' (z|f) Ood ' matches ' zood ' or ' food '.
[XYZ]
Character set combination. Matches any one of the characters contained. For example, ' [ABC] ' can match ' a ' in ' plain '.
[^XYZ]
Negative character set combination. Matches any characters that are not included. For example, ' [^ABC] ' can match ' P ' in ' plain '.
[A-z]
The range of characters. Matches any character within the specified range. For example, ' [A-z] ' can match any lowercase alphabetic character in the range ' a ' to ' Z '.
[^a-z]
Negative character range. Matches any character that is not in the specified range. For example, ' [^a-z] ' can match any character that is not in the range of ' a ' to ' Z '.
\b
Matches a word boundary, which is the position between the word and the space. For example, ' er\b ' can match ' er ' in ' never ', but cannot match ' er ' in ' verb '.
\b
Matches a non-word boundary. ' er\b ' can match ' er ' in ' verb ', but cannot match ' er ' in ' Never '.
\cx
Matches the control character indicated by X. For example, \cm matches a control-m or carriage return character. The value of x must be one-a-Z or a-Z. Otherwise, c is treated as a literal ' C ' character.
\d
Matches a numeric character. equivalent to [0-9].
\d
Matches a non-numeric character. equivalent to [^0-9].
\f
Matches a page feed character. Equivalent to \x0c and \CL.
\ n
Matches a line feed character. Equivalent to \x0a and \CJ.
\ r
Matches a carriage return character. Equivalent to \x0d and \cm.
\s
Matches any white space character, including spaces, tabs, page breaks, and so on. equivalent to [\f\n\r\t\v].
\s
Matches any non-white-space character. equivalent to [^ \f\n\r\t\v].
\ t
Matches a tab character. Equivalent to \x09 and \ci.
\v
Matches a vertical tab. Equivalent to \x0b and \ck.
\w
Matches any word character that includes an underscore. Equivalent to ' [a-za-z0-9_] '.
\w
Matches any non word character. Equivalent to ' [^a-za-z0-9_] '.
\xn
Matches n, where n is the hexadecimal escape value. The hexadecimal escape value must be a determined two digits long. For example, ' \x41 ' matches ' A '. ' \x041 ' is equivalent to ' \x04 ' & ' 1 '. You can use ASCII encoding in regular expressions ...
\num
Matches num, where num is a positive integer. A reference to the match that was obtained. For example, ' (.) ' matches two consecutive identical characters.
\ n
Identifies a octal escape value or a back reference. N is a back reference if you have at least N obtained subexpression before. Otherwise, if n is an octal number (0-7), then N is an octal escape value.
\nm
Identifies a octal escape value or a back reference. NM is a \nm if at least one of the preceded by the at least NM gets the subexpression before the If there are at least N fetches before \nm, then N is a back reference followed by a literal m. If all the preceding conditions are not satisfied, if both N and M are octal digits (0-7), then \nm will match octal escape value nm.
\nml
If n is an octal number (0-3) and both M and L are octal digits (0-7), the octal escape value NML is matched.
\un
Matches n, where N is a Unicode character represented in four hexadecimal digits. For example, \u00a9 matches the copyright symbol (?).