php regular expression

This article introduces regular expressions in php, and I would like to share them with you. Friends who are interested can take a look at

• The role of regular expressions
  Split, search, match, replace string

• ##Separator

  
  

• Forward slash (/)

• hash symbol (#)

##Negative symbol (~)

Universal Atom

• 
  

##\d
• Decimal 0 to 9

\D
• Negate decimal numbers from 0 to 9

\w
• Numbers and letters underline

\W
• In addition to numbers and letters underline

\s
• White space characters

\S
• Except whitespace characters

• 
  

.
Matches any single character except newline characters (\n, \r)

• *
Matches the previous subexpression zero or more times

• +
Matches the previous subexpression one or more times

• ?
Matches the previous subexpression zero or one time

• {n}
n is a non Negative integer, matches a certain number of n times

• ##{n,}

  n is a non-negative integer, matches at least n times

• {n,m}

  m and n are both non-negative integers, where n <= m. Match at least n times and match at most m times

• ^

  Match the beginning of the input string

• $

  Matches the end position of the input string

• []

  represents matching an element in a set, such as [abc] represents matching a or b or c

• ()

  Match the content within () and get
##Pattern modifier

• 
  i

  Case-insensitive

• m Treat the string as multiple lines, no matter which line it is, it can match

• s Treat the string as a single line, and the newline character is treated as an ordinary character

• e e Use with function preg_replace() (php7 to cancel)

• U U Only match the most recent string, no repeated matches

• x x Ignore whitespace in the pattern

• A Force matching from the beginning of the target string

• D If you use $ to limit the ending character, no newline at the end is allowed

• u The pattern string is treated as UTF-8 (can be used to match Chinese)

To be continued……………………

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