Regular expression System tutorial (V) _php Tutorial

5. All symbols explained

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http://www.bkjia.com/PHPjc/532537.html www.bkjia.com true http://www.bkjia.com/PHPjc/532537.html techarticle 5. Full symbol explanation character description marks the next character as a special character, or a literal character, or a backward reference, or an octal escape character. For example, n matches the word ...

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character	Description
	Marks the next character as a special character, or a literal character, or a backward reference, or an octal escape. For example, n matches the character "n". Matches a line break. Sequence \ Match "" and "(" Then Match "(".
^	Matches the starting position of the input string. If the Multiline property of the RegExp object is set, ^ also matches or follows the position.
$	Matches the end position of the input string. If the Multiline property of the RegExp object is set, $ also matches or precedes the position.
*	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. For example, "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+? A single "O" will be matched, and o+ will match all O.
.	Matches any single character except "". To match any characters that are included, use a pattern like [.].
(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 the $0...$9 property is used in JScript. 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 in Windows 2000, but it does not match Windows 3.1. 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	A negative pre-check matches the lookup string at the beginning of any string that does not match 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 in Windows 3.1, but it does not match Windows 2000. 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 range A to Z.
[^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.
	Matches a word boundary, which is the position between a word and a space. For example, er can match the ER in "never", but not the ER in "verb".
B	Matches a non-word boundary. The ErB can match the ER in "verb", but not the 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 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.
	Matches a line break. Equivalent to x0a and CJ.
	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 [FV].
S	Matches any non-whitespace character. equivalent to [^ FV].
	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:
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