PHP regular expression full tutorial to improve the article, regular expression full tutorial

PHP regular expression full tutorial to improve the article, regular expression full tutorial

In the previous article, I shared with you the basics of the php Regular Expression Security tutorial. This article will continue with the knowledge of php regular expressions. For details, see the following.

Priorities of various operators in php Regular Expressions

Operations with the same priority are performed from left to right. Operations with different priorities are first high and then low. The priorities of operators are as follows:

Operator description

Escape Character

(),(? :),(? =), [] Parentheses and square brackets

*, + ,?, {N}, {n ,}, {n, m} qualifier

^, $, Anymetacharacter location and Sequence

| "Or" Operation

Php regular expression.

Character Description

Mark the next character as a special character, a literal character, or a backward 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 start position of the input string. If the Multiline attribute of the RegExp object is set, ^ matches the position after 'n' or 'R.

$ Matches the end position of the input string. If the Multiline attribute of the RegExp object is set, $ also matches the location before 'n' or 'R.

* Matches the previous subexpression zero or multiple times. For example, zo * can match "z" and "zoo ". * Is equivalent to {0 ,}.

+ Match the previous subexpression once or multiple times. For example, 'Zo + 'can match "zo" and "zoo", but cannot match "z ". + Is equivalent to {1 ,}.

? Match the previous subexpression zero or once. For example, "do (es )? "Can match" do "in" do "or" does ".? It is equivalent to {0, 1 }.

{N} n is a non-negative integer. Match 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 *'.

Both {n, m} m and n are non-negative integers, where n <= m. Match at least n times and at most m times. For example, "o {1, 3}" matches the first three o in "fooooood. 'O {0, 1} 'is equivalent to 'o? '. Note that there must be no space between a comma and two numbers.

? When this character is followed by any other delimiter (*, + ,?, The matching mode after {n}, {n ,}, {n, m}) is not greedy. The non-Greedy mode matches as few searched strings as possible, while the default greedy mode matches as many searched strings as possible. For example, for strings "oooo", 'O ++? 'Will match a single "o", and 'O +' will match all 'O '.

. Match any single character except "n. To match any character including 'n', use a pattern like '[. n.

(Pattern) matches pattern and obtains this match. The obtained match can be obtained from the generated Matches set. The SubMatches set is used in VBScript, and $0… is used in JScript... $9 attribute. To match parentheses, use '(' or ')'.

(? : Pattern) matches pattern but does not get the matching result. That is to say, this is a non-get match and is not stored for future use. This is useful when you use the "or" character (|) to combine each part of a pattern. For example, 'industr (? : Y | ies) is a simpler expression than 'industry | industries.

(? = Pattern) Forward pre-query: matches the search string at the beginning of any string that matches pattern. This is a non-get match, that is, the match does not need to be obtained for future use. For example, 'windows (? = 95 | 98 | NT | 2000) 'can match "Windows" in "Windows 2000", but cannot match "Windows" in "Windows 3.1 ". Pre-query does not consume characters, that is, after a match occurs, the next matching search starts immediately after the last match, instead of starting after the pre-query characters.

(?! Pattern) negative pre-query: matches the search string at the beginning of any string that does not match pattern. This is a non-get match, that is, the match does not need to be obtained for future use. For example, 'windows (?! 95 | 98 | NT | 2000) 'can match "Windows" in "Windows 3.1", but cannot match "Windows" in "Windows 2000 ". Pre-query does not consume characters, that is, after a match occurs, the next matching search starts immediately after the last match, instead of starting after the pre-query characters.

X | y matches x or y. For example, 'z | food' can match "z" or "food ". '(Z | f) ood' matches "zood" or "food ".

[Xyz] Character Set combination. Match any character in it. For example, '[abc]' can match 'A' in "plain '.

[^ Xyz] combination of negative character sets. Match any character not included. For example, '[^ abc]' can match 'p' in "plain '.

[A-z] character range. Matches any character in the specified range. For example, '[a-z]' can match any lowercase letter in the range of 'A' to 'Z.

[^ A-z] negative character range. Matches any character that is not within 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, that is, the position between a word and a space. For example, 'erb' can match 'er' in "never", but cannot match 'er' in "verb '.

B matches non-word boundaries. 'Erb' can match 'er' in "verb", but cannot match 'er' in "never '.

Cx matches the control characters specified by x. For example, cM matches a Control-M or carriage return character. The value of x must be either a A-Z or a-z. Otherwise, c is treated as an original 'C' character.

D matches a numeric character. It is equivalent to [0-9].

D. match a non-numeric character. It is equivalent to [^ 0-9].

F matches a form feed. It is equivalent to x0c and cL.

N matches a linefeed. It is equivalent to x0a and cJ.

R matches a carriage return. It is equivalent to x0d and cM.

S matches any blank characters, including spaces, tabs, and page breaks. It is equivalent to [fnrtv].

S matches any non-blank characters. It is equivalent to [^ fnrtv].

T matches a tab. It is equivalent to x09 and cI.

V matches a vertical tab. It is equivalent to x0b and cK.

W matches any word characters that contain underscores. It is equivalent to '[A-Za-z0-9 _]'.

W matches any non-word characters. It is equivalent to '[^ A-Za-z0-9 _]'.

Xn matches n, where n is the hexadecimal escape value. The hexadecimal escape value must be determined by the length of two numbers. For example, 'x41' matches "". 'X041' is equivalent to 'x04 '& "1 ". The regular expression can use ASCII encoding ..

Num matches num, where num is a positive integer. References to the obtained matching. For example, '(.) 1' matches two consecutive identical characters.

N identifies an octal escape value or a backward reference. If there are at least n obtained subexpressions before n, n is backward referenced. Otherwise, if n is an octal digit (0-7), n is an octal escape value.

Nm identifies an octal escape value or a backward reference. If at least one child expression is obtained before nm, then nm is backward referenced. If at least n records are obtained before nm, n is a backward reference followed by text m. If none of the preceding conditions are met, if n and m are Octal numbers (0-7), nm matches the octal escape value nm.

If n is an octal digit (0-3) and m and l are octal numerals (0-7), nml matches the octal escape value nml.

Un matches n, where n is a Unicode character represented by four hexadecimal numbers. For example, u00A9 matches the copyright symbol (?).

The above content is an improvement article on the PHP Regular Expression complete tutorial. I hope you will like it.