PHP Regular Expression Summary _php tutorial

Summary of regular expressions in PHP

　　Two common regular functions in 1.PHP

A.preg_match regular functions, based on the Perl language

Syntax: Preg_match (mode,string Subject,array matches)

Description: The mode parameter----regular module, which is the regular expression (syntax)

The contents of the subject parameter----regular

Matches parameter----The result of a regular (get the form of an array)

B.ereg regular function to POSIX basis (Unix, Script)

Syntax: Ereg (mode, string subject, array regs)

　　2. Elements included in a regular expression

A. Atoms (ordinary characters: A-Z-A-0-9, atomic tables, escape characters)

B. metacharacters (characters with special features, such as: #, *)

C. Pattern modifier (System built-in part character I, M, S, U ...)

　　3. "Atoms" in regular expressions

A.a-z A-Z _ 0-9//most common characters

B. (ABC) (SKD)//cell symbol enclosed in parentheses (one whole)

C.[ABCS][^ABD]//The atomic table enclosed in square brackets, the ^ in the atomic table represents the excluded or opposite content

D. Escape character

\d contains all the numbers [0-9]

\d except all numbers [^0-9]

\w includes all English characters [A-Z A-Z 0-9]

\w except for all English characters [^a-z A-Z 0-9]

\s return, line change, etc.

......

Note: Parentheses must be the whole to match; Square brackets can match as long as they are subsets (content exists)

　　4. Regular expression meta-characters

* Match the previous content 0 times 1 or more times

. Matches content 0 times 1 times or more, but does not include carriage returns (substituting for yourself, anything)

+ match 1 or more times of previous content

? Match the previous content 0 or 1 times

| Select match like in PHP | (because this operation conforms to the weak type leading to the most overall match, similar to a word match)

^ Match String header contents

$ match String Trailing content

\b Matches a word boundary, which can be either a space or a special match (with a word delimiter, like a space)

\b Match exception with word boundary unexpected content (no word delimiter)

{m} matches the previous content with a repeat number of M times

{m,} The number of repetitions of the previous content is greater than or equal to M times

{M,n} matches the number of repetitions of the previous content m times to N times

() merge the whole match, and put in memory, can use \\1 \\2 ... Get (call to put in-memory content)

　　5. Sequence of operations

Still follow the arithmetic rules from left to right

Priority level:

() parentheses because it is memory processing, so the highest

* ? + {} Repeat match content next

^ $ \b Border Processing third

| Condition Processing IV

Finally, the matching is calculated in order of operation

　　6. Mode modifier

A pattern modifier is a feature that is enhanced and supplemented for regular expressions and is used outside of the regular for example:/Regular/U

Common modifiers:

I regular content is not case-sensitive at match time (by default it is differentiated)

M uses multi-line recognition matching when matching first content or tail content

S will escape carriage return cancellation is for a single line match as. Match the time

x ignores whitespace in the regular

A Force A match from the beginning

D force $ match tail without any content \ n

U disallow greedy match to trace only to the nearest match and end, regular expression commonly used on the collector

　　7. Matching function

Preg_match_all All matching functions

Syntax: Preg_match_all (string pattern, string subject, array matches [, int flags])

Description: Sort the results to make $matches [0] match the number of all patterns

Purpose: Intercept more detailed content, collect Web pages, analyze text

　　8. Replacement function

Preg_replace Regular Replacement function

Syntax: preg_replace (mixed pattern, mixed replacement, mixed subject [, int limit])

Description: Replace the relevant content with a regular expression, similar to the previously learned str_replace string substitution, but the function is stronger than it

Hint: 1, the replacement content can be a regular or an array of regular

2, the replacement content can be replaced by the modifier e to resolve the content of the execution

Purpose: Replace some of the more complex content, also can be used for the conversion of content

　　9. Split function

Preg_split Regular Cutting

Syntax: Preg_split (string pattern, string subject [, int limit [, int flags]])

Description: Cutting related content with regular expressions, similar to the explode cutting function previously learned, but explode can only be cut in one way with limitations.

http://www.bkjia.com/PHPjc/957532.html www.bkjia.com true http://www.bkjia.com/PHPjc/957532.html techarticle PHP Regular Expression Summary 1.PHP two commonly used regular function A.preg_match regular function, the Perl language as the base syntax: Preg_match (mode,string subject,array matches) Description: Mo ...

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