Special symbols in a regular expression in PHP

Characters
Meaning: For a character, it is usually expressed as literal meaning that the next character is a special character and is not interpreted.
For example:/b/matches the character ' B ', by adding a backslash in front of B, which is/b/, the character becomes a special character, indicating
Match the dividing line of a word.
Or:
For several characters, the usual description is special, which indicates that the characters immediately followed are 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 represents the match must be at the front.
For example:/^a/does not match "an A," in the ' 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 preceding character 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 '
Any characters in the runted ".

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

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

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


Character (x)
Meaning: Match ' x ' and record the matching value.
For example:/(foo)/Match and record "Foo bar." In the ' foo '. The matched substring can be in the result array of the vegetarian [1], ..., [n] Return
Back, or the property of the RegExp object, ..., returns.

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

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

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

character [^XYZ]
Meaning: A character complement, that is, it matches everything except the listed characters. You can use hyphens-to indicate a range of characters.
For example: [^ABC] and [^a-c] are equivalent, they first match ' 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 (do not confuse)
For example:/bnw/matches ' no ' in ' Noonday ',/wyb/matches ' possibly yesterday. ' In the ' ly '.

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

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

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

Character F
Meaning: Match a single form character

Character N
Meaning: Match a line break

Character R
Meaning: Match a carriage return character

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

Character S
Meaning: matches a single character except white space, 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 as well as underscores, equivalent to [a-za-z0-9_].
For example:/w/matches "Apple," in the ' a ', ". 28," In the ' 5 ' and ' 3D. ' 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: n Here 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/matches "Apple, orange, cherry, peach." In the ' Apple, Orange ', here's a more complete example.
Note: If the number in the left parenthesis is smaller than the number specified by N, then N takes a line of octal escape as a description.

Characters Ooctal and Xhex
Meaning: The ooctal here is an octal escape value, while Xhex is a hexadecimal escape value that allows the embedding of ASCII code 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
\
The next character is marked with a special character, or a literal character, or a back reference, or an octal escape character. For example, ' n ' matches the character "n". ' \ n ' matches a line break. The sequence ' \ ' matches "" and "\ (" Matches "(".
^
Matches the starting 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, $ also matches the position before ' \ n ' or ' \ R '.
*
Matches the preceding subexpression 0 or more times. For example, zo* can match "z" and "Zoo". * Equivalent to {0,}.
+ matches the preceding subexpression one or more times. For example, ' zo+ ' can match "Zo" and "Zoo", but not "Z". + equivalent to {1,}.
?
Matches the preceding subexpression 0 or one time. For example, "Do (es)?" can match "do" in "do" or "does".? 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}
Both M and n are non-negative integers, where n <= m. Matches at least n times 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? '. Note that there can be no spaces between a comma and two numbers.
?
When the character immediately follows any other restriction (*, +,?, {n}, {n,}, {n,m}), the matching pattern is non-greedy. The non-greedy pattern matches the searched string as little 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", while ' 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, the Submatches collection is used in VBScript, and {CONTENT} is used in JScript ... Property. To match the parentheses character, use ' \ (' or ' \ ').
(?:p Attern)
Matches pattern but does not get a matching result, which means that this is a non-fetch match and is not stored for later use. This is useful when using the "or" character (|) to combine parts of a pattern. For example, ' Industr (?: y|ies) is a more abbreviated expression than ' industry|industries '.
(? =pattern)
Forward-checking matches the lookup string at the beginning of any string that matches the pattern. This is a non-fetch match, which means that the match does not need to be acquired for later use. For example, ' Windows (? =95|98| nt|2000) ' Can match Windows 2000 ', but does not match Windows 3.1 in Windows. Pre-checking does not consume characters, that is, after a match occurs, the next matching search starts immediately after the last match, rather than starting with the character that contains the pre-check.
(?! Pattern
Negative to pre-check, in any mismatch negative lookahead matches the search string at any point where a string of not matching pattern begins to match the lookup strings. This is a non-fetch match, which means that the match does not need to be acquired for later use. For example ' Windows (?! 95|98| nt|2000) ' can match Windows 3.1 ', but does not match Windows 2000 in Windows. Pre-check does not consume characters, that is, after a match occurs, the next matching search starts immediately after the last match, rather than starting with 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]
The character set is combined. Matches any one of the characters contained. For example, ' [ABC] ' can match ' a ' in ' plain '.
[^XYZ]
Negative character set. Matches any character that is not contained. For example, ' [^ABC] ' can match ' P ' in ' plain '.
[A-z]
The character range. Matches any character within the specified range. For example, ' [A-z] ' can match any lowercase alphabetic character in the ' a ' to ' Z ' range.
[^a-z]
A negative character range. Matches any character that is not in the specified range. For example, ' [^a-z] ' can match any character that is not within the range of ' a ' to ' Z '.
\b
Matches a word boundary, which is the position between a word and a space. For example, ' er\b ' can match ' er ' in ' never ', but not ' 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. The value of x must be one of 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 break. Equivalent to \x0c and \CL.
\ n
Matches a line break. Equivalent to \x0a and \CJ.
\ r
Matches a carriage return character. Equivalent to \x0d and \cm.
\s
Matches any whitespace character, including spaces, tabs, page breaks, and so on. equivalent to [\f\n\r\t\v].
\s
Matches any non-whitespace 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
Match N, where n is the hexadecimal escape value. The hexadecimal escape value must be two digits long for a determination. For example, ' \x41 ' matches ' A '. ' \x041 ' is equivalent to ' \x04 ' & ' 1 '. ASCII encoding can be used in regular expressions:
\num
Matches num, where num is a positive integer. A reference to the obtained match. For example, ' (.) ' matches two consecutive identical characters.
\ n
Identifies an octal escape value or a back reference. N is a back reference if \ n has at least one of the first obtained sub-expressions. Otherwise, if n is the octal number (0-7), N is an octal escape value.
\nm
Identifies an octal escape value or a back reference. If at least \nm was preceded by at least nm, then NM is a back reference. If there are at least N fetches before \nm, then N is a back reference followed by the literal m. If none of the preceding conditions are met, if both N and M are octal digits (0-7), then \nm will match the 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
Match N, where N is a Unicode character represented by four hexadecimal digits. For example, \u00a9 matches the copyright symbol (?).

Special symbols in a regular expression in PHP