PHP regular expression basic functions_PHP tutorial

WBOY
Release: 2016-07-20 11:17:53
Original
850 people have browsed it

Characters that need to be escaped in PHP regular expressions are as follows:

 $^*()+={}[]|/:<>.?'"

Note: Perl-style expressions require that they start and end with /, such as: /food/ matches the character food

Perl modifiers are as follows:

i Complete case-insensitive search

g Find all occurrences (complete global search)

m Treats a string as multiple lines (m means multiple). By default, the ^ and $ characters match the very beginning and the very end of a string. Using the m modifier will cause ^ and $ to match the beginning of each line in the string

s Treats a string as a line, ignoring all newlines; it is the opposite of the m modifier

x Ignore whitespace and comments in php regular expressions

U Stop after the first match. By default, the last matching character result will be found. Use this modifier to stop after the first match. Then form loop matching.

Metacharacter description:

Another useful thing you can do with Perl regular expressions is to use various metacharacters to search for matches. A metacharacter is an alphabetic character preceded by a backslash, which represents a special meaning. The following are some useful metacharacters.

A only matches the beginning of the string

b matches word boundaries

 B matches any character

outside word boundaries

 d matches numeric characters, which is the same as [0-9]

 D PHP regular matching non-numeric characters

s matches whitespace characters

S PHP regular matching non-whitespace characters

 [] surrounds a character class, which includes: [0-9] [a-z] [a-zA-Z] and the like.

 () surrounds a character group or defines a backreference

 $ matches the end of the line

 ^ Matches the beginning of the line

 * Matches the preceding subexpression zero or more times. To match * characters, use *

 + Matches the previous subexpression one or more times. To match the + character, use +

? Match the preceding subexpression zero or once, or specify a non-greedy qualifier ?

. Matches any character

except newline

Introduces the next metacharacter

 w matches any string containing only underscores and alphanumeric characters, which is the same as [a-zA-Z0-9_]

 W PHP regular matching strings without underscores and alphanumeric characters

Perl style functions are:

 array preg_grep(string pattern, array input [, flags])

Search for all elements in the array and return an array consisting of all elements matching a certain pattern

PHP 4.3 added an optional parameter flag, which accepts a value PREG_GREP_INVERT. Passing this flag will get data elements that do not match the pattern.

 int preg_match(string pattern, string string [, array matches [, int flags [, int offset]]])

Search for the pattern in the string, returning TRUE if it exists, otherwise returning FALSE.

The optional input parameter matches can contain parts of sub-patterns contained in the search pattern. The matched string is returned by default. When surrounded by () sub-characters, it will be output after the array.

 int preg_match_all(string pattern, string string, array pattern_array [, int order])

It is the same as the function preg_match, but preg_match only searches once, while preg_match_all will perform a loop search and return all matching results.

 mixed preg_replace(mixed pattern, mixed replacement, mixed str [, int limit])

Replaces all occurrences of pattern with replacement and returns the modified result.

Optional limit specifies how many matches should occur. Not setting limit or setting it to -1 will replace all occurrences.

The above are commonly used functions, and there are also detailed explanations such as preg_quote, preg_replace_callbak, preg_split, etc. . .

www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/371877.htmlTechArticleThe characters that need to be escaped in PHP regular expressions are as follows: $^*()+={}[] |/:.?' Note: Perl style expressions require that they start and end with /, such as: /food/ table matches the character food perl modifier such as...
source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template
About us Disclaimer Sitemap
php.cn:Public welfare online PHP training,Help PHP learners grow quickly!