PHP正则表达式：如何匹配\\ r和\\ n而不使用[\\ r \\ n]？

Question

I have tested \\v (vertical white space) for matching \\r\\n and their combinations, but I found out that \\v does not match \\r and \\n . Below is my code that I am using..

$string = "
Test
";

if (preg_match("#\v+#", $string )) {
  echo "Matched";
} else {
  echo "Not Matched";
}

To be more clear, my question is, is there any other alternative to match \\r\\n ?

Answer 1

PCRE and newlines

PCRE has a superfluity of newline related escape sequences and alternatives.

Well, a nifty escape sequence that you can use here is \\R . By default \\R will match Unicode newlines sequences, but it can be configured using different alternatives.

To match any Unicode newline sequence that is in the ASCII range.

preg_match('~\R~', $string);

This is equivalent to the following group:

(?>\r\n|\n|\r|\f|\x0b|\x85)

---

To match any Unicode newline sequence; including newline characters outside the ASCII range and both the line separator ( U+2028 ) and paragraph separator ( U+2029 ), you want to turn on the u ( unicode ) flag.

preg_match('~\R~u', $string);

The u ( unicode ) modifier turns on additional functionality of PCRE and Pattern strings are treated as ( UTF-8 ).

The is equivalent to the following group:

(?>\r\n|\n|\r|\f|\x0b|\x85|\x{2028}|\x{2029})

---

It is possible to restrict \\R to match CR , LF , or CRLF only:

preg_match('~(*BSR_ANYCRLF)\R~', $string);

The is equivalent to the following group:

(?>\r\n|\n|\r)

Additional

Five different conventions for indicating line breaks in strings are supported:

(*CR)        carriage return
(*LF)        linefeed
(*CRLF)      carriage return, followed by linefeed
(*ANYCRLF)   any of the three above
(*ANY)       all Unicode newline sequences

---

Note : \\R does not have special meaning inside of a character class. Like other unrecognized escape sequences, it is treated as the literal character "R" by default.

Answer 2

This doesn't answer the question for alternatives, because \\v works perfectly well

\\v matches any character considered vertical whitespace; this includes the platform's carriage return and line feed characters (newline) plus several other characters, all listed in the table below.

You only need to change "#\\v+#" to either

• "#\\\\v+#" escape the backslash

or

• '#\\v+#' use single quotes

In both cases, you will get a match for any combination of \\r and \\n .

Update:

Just to make the scope of \\v clear in comparison to \\R , from perlrebackslash

• \\R
  \\R matches a generic newline; that is, anything considered a linebreak sequence by Unicode. This includes all characters matched by \\v (vertical whitespace), ...

Answer 3

If there is some strange requirement that prevents you from using a literal [\\r\\n] in your pattern, you can always use hexadecimal escape sequences instead:

preg_match('#[\xD\xA]+#', $string)

This is pattern is equivalent to [\\r\\n]+ .

Answer 4

To match every LINE of a given String, simple use the ^$ Anchors and advice your regex engine to operate in multi-line mode. Then ^$ will match the start and end of each line, instead of the whole strings start and end.

http://php.net/manual/en/reference.pcre.pattern.modifiers.php

in PHP, that would be the m modifier after the pattern. /^(.*?)$/m will simple match each line, seperated by any vertical space inside the given string.

Btw: For line-Splitting, you could also use split() and the PHP_EOL constant:

$lines = explode(PHP_EOL, $string);

Answer 5

The problem is that you need the multiline option, or dotall option if using dot. It goes at the end of the delimiter.

http://www.php.net/manual/en/regexp.reference.internal-options.php

$string = "
Test
";
if(preg_match("#\v+#m", $string ))
echo "Matched";
else
echo "Not Matched";

Answer 6

To match a newline in PHP, use the php constant PHP_EOL . This is crossplatform.

if (preg_match('/\v+' . PHP_EOL ."/", $text, $matches ))
   print_R($matches );

Answer 7

This regex also matches newline \\n and carriage return \\r characters.

(?![ \t\f])\s

DEMO

To match one or more newline or carriage return characters, you could use the below regex.

(?:(?![ \t\f])\s)+

DEMO