PHP regular expression special character _ PHP Tutorial-php Tutorial

Special characters in PHP regular expressions. Character meaning: for a character, it usually indicates the literal meaning, indicating that the subsequent character is a special character, not interpreted. For example, B matches the character 'B' by adding a backslash before B. Character/
Meaning: for characters, it usually indicates the literal meaning, indicating that the subsequent characters are special characters, not explained.
For example, if/B/matches the character 'B' and adds a backslash (/B/) before B, the character becomes a special character, the line that matches a word.
Or:
For a few characters, it is generally described as special. it is pointed out that the subsequent characters are not special, but should be interpreted literally.
For example, * is a special character that matches any character (including 0 characters). For example,/a */indicates that it matches 0 or multiple a characters. To match the literal *, add a backslash before a. For example,/a */matches 'A *'.

Character ^
Meaning: the matched characters must be at the frontend.
For example,/^ A/does not match 'A' in "an A,", but matches 'A' in the top of "An '.

Character $
Meaning: similar to ^, it matches the last character.
For example,/t $/does not match 't' in "eater", but matches 't' in "eat '.

Character *
Meaning: match the first character of * 0 or n times.
For example,/bo */matches 'boooo' in "A ghost booooed" or 'B' in "A bird warbled", but does not match "Agoat g
Any character in runted.

Character +
Meaning: match the character before the plus sign once or n times. It is equivalent to {1 ,}.
For example,/a +/matches all 'A' in "candy" and "caaaaaaandy '.

Character?
Meaning: match? The first character is 0 or 1 time.
Example:/e? Le? /Match 'El' in "angel" and 'le' in "angle '.

Character.
Meaning: (decimal point) match all single characters except line breaks.
For example,/. n/matches 'any' and 'on' in "nay, an apple is on the tree", but does not match 'nay '.

Character (x)
Meaning: Match 'X' and record the matched value.
For example,/(foo)/matches and records 'foo' in "foo bar '. Matching substrings can be returned by the element [1],..., [n] in the result array.
Return, or be returned by RegExp object attributes.

Character x │ y
Meaning: Match 'X' or 'y '.
For example,/green │ red/matches 'green' in "green apple" and 'red' in "red apple '.

Character {n}
Meaning: Here n is a positive integer. Match the previous n characters.
For example:/a {2}/does not match 'A' in "candy,", but matches all 'A' and "caaandy" in "caandy. "The first two 'A '.

Character {n ,}
Meaning: Here n is a positive integer. Match at least n first characters.
For example,/a {2,} does not match 'A' in "candy", but matches all 'A' in "caandy" and "caaaaaaandy'

Character {n, m}
Meaning: both n and m are positive integers. Match at least n characters at most before m.
For example,/a {}/does not match any character in "cndy", but matches the first two characters in "candy," 'A', "caandy ,"
'A' and "caaaaaaandy" are the first three 'A'. note: even if "caaaaaaandy" has many 'A ', but only match the first three 'A', that is, "aaa ".

Character [xyz]
Meaning: a one-character list that matches any character in the list. You can use a hyphen to indicate a character range.
For example, [abcd] is the same as [a-c. They match 'B' in "brisket" and 'C' in "ache '.

Character [^ xyz]
Meaning: A character complement, that is, it matches everything except the listed characters. You can use a hyphen to indicate the one-character range.
For example, [^ abc] is equivalent to [^ a-c]. they first match 'R' in "brisket" and 'H' in "chop '.

Character
Meaning: match a space (do not confuse with B)

Character B
Meaning: match the boundary of a word, such as a space (not to be confused)
For example,/bnw/matches 'no' in "noonday",/wyb/matches 'ly 'in "possibly yesterday '.

Character B
Meaning: match the non-dividing line of a word
For example,/wBn/matches 'on' in "noonday",/yBw/matches 'Ye 'in "possibly yesterday '.

Character cX
Meaning: X is a control character. Matches the control character of a string.
For example,/cM/matches control-M in a string.

Character d
Meaning: matching a number is equivalent to [0-9].
For example,/d/or/[0-9]/matches '2' in "B2 is the suite number '.

Character D
Meaning: match any non-number, which is equivalent to [^ 0-9].
For example,/D/or/[^ 0-9]/matches 'B' in "B2 is the suite number '.

Character f
Meaning: match a form character

Character n
Meaning: match a linefeed.

Meaning: for characters, it usually indicates the literal meaning, indicating that the subsequent characters are special characters, not explained. For example:/B/match the character 'B', add a backslash before B...