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List of special characters in regular expressions_PHP Tutorial
- WBOYOriginal
- 2016-07-13 17:34:521024browse
Special characters in regular expressions:
Character
Meaning: For characters, it usually means literal meaning, indicating that the following characters are special characters without explanation.
For example: /b/ matches the character b. By adding a backslash in front of b, which is /b/, the character becomes a special character, which means
Match a word's boundary.
Or:
For several characters, the specification is usually special, indicating that the following characters are not special and should be interpreted literally.
For example: * is a special character, matching any number of characters (including 0 characters); for example: /a*/ means matching 0 or more a's.
To match a literal *, precede a with a backslash; for example: /a*/ matches a*.
Character ^
Meaning: Indicates that the matching character must be at the front.
For example: /^A/ does not match the A in "an A," but matches the first A in "An A.".
Character $
Meaning: Similar to ^, matches the last character.
For example: /t$/ does not match the t in "eater", but does match the t in "eat".
Characters*
Meaning: Match the character before * 0 or n times.
For example: /bo*/ matches the boooo in "A ghost booooed" or the b in "A bird warbled", but does not match "A goat g
runted".
Character +
Meaning: Match the character before the + sign 1 or n times. Equivalent to {1,}.
For example: /a+/ matches a in "candy" and all a's in "caaaaaaandy."
Character?
Meaning: Match the character before ? 0 or 1 times.
For example: /e?le?/ matches el in "angel" and le in "angle.".
Character.
Meaning: (decimal point) matches all single characters except newline characters.
For example: /.n/ matches an and on in "nay, an apple is on the tree", but does not match nay.
Character(x)
Meaning: Match x and record the matching value.
For example: /(foo)/ matches and records foo in "foo bar." The matching substring can be returned by the elements [1], ..., [n] in the result array
Returned, or returned by the properties $1, ..., $9 of the RegExp object.
Character x|y
Meaning: Match x or y.
For example: /green|red/ matches the green in "green apple" and the red in "red apple.".
Character {n}
Meaning: n here is a positive integer. Matches the first n characters.
For example: /a{2}/ does not match the a in "candy,", but matches all a in "caandy," and the first two
in "caaandy."
a.
Character {n,}
Meaning: n here is a positive integer. Matches at least n previous characters.
For example: /a{2,} does not match a in "candy", but matches all a in "caandy" and all a in "caaaaaaandy."
Character {n,m}
Meaning: n and m here are both positive integers. Matches at least n and at most m previous characters.
For example: /a{1,3}/ does not match any characters in "cndy", but matches the a in "candy," and the first two
in "caandy,"
a and the first three a's in "caaaaaaandy", note: even if there are many a's in "caaaaaaandy", only the first three a's are matched
An a is "aaa".
Character[xyz]
Meaning: A list of characters, matching any character in the list. You can specify a range of characters using the hyphen -.
For example: [abcd] is the same as [a-c]. They match the b in "brisket" and the c in "ache".
Character[^xyz]
Meaning: The one-character complement, that is, it matches everything except the listed characters. You can use hyphens - point out one
Character range.
For example: [^abc] and [^a-c] are equivalent. They match the r in "brisket" and the h in "chop." at the earliest.
Character[b]
Meaning: Matches a space (not to be confused with b)
Character b
Meaning: Match a word boundary, such as a space (not to be confused with [b])
For example: /bnw/ matches no in "noonday", /wyb/ matches ly in "possibly yesterday."
Character B
Meaning: Match the non-breaking line of a word
For example: /wBn/ matches on in "noonday", /yBw/ matches ye in "possibly yesterday."
Character cX
Meaning: The X here is a control character. Matches a string of control characters.
For example: /cM/ matches control-M in a string.
Character d
Meaning: Match a number, equivalent to [0-9].
For example: /d/ or /[0-9]/ matches 2 in "B2 is the suite number.".
Character D
Meaning: Matches any non-number, equivalent to [^0-9].
For example: /D/ or /[^0-9]/ matches B in "B2 is the suite number.".
Character f
Meaning: Match a form character
Character n
Meaning: Matches a newline character
Character r
Meaning: Match a carriage return character
Characters
Meaning: Matches a single white space character, including space, tab, form feed, and newline character, equivalent to [fnrtv].
For example: /sw*/ matches bar in "foo bar."
Character S
Meaning: Matches a single character other than white space, equivalent to [^ fnrtv].
For example: /S/w* matches foo in "foo bar."
Character t
Meaning: Match a tab character
Character v
Meaning: Matches a leading tab character
Character w
Meaning: Matches all numbers, letters and underscores, equivalent to [A-Za-z0-9_].
For example: /w/ matches the a in "apple,", the 5 in "$5.28," and the 3 in "3D.".
Character W
Meaning: Matches other characters except numbers, letters and underscores, equivalent to [^A-Za-z0-9_].
For example: /W/ or /[^$A-Za-z0-9_]/ matches the % in "50%.".
Character n
Meaning: n here is a positive integer. The value of n that matches the last substring of a regular expression (counting left parentheses).
For example: /apple(,)sorange1/ matches apple, orange in "apple, orange, cherry, peach.", below
There is a more complete example.
Note: If the number in the left parenthesis is smaller than the number specified by n, n takes the octal escape of the next line as the description.
Characters ooctal and xhex
Meaning: ooctal here is an octal escape value, and xhex is a hexadecimal escape value, allowing ASCII codes to be embedded in a regular expression.