正则表达式与换行符不匹配

Question

One of these days where I'm about to question my sanity again...

I don't understand why my regex refuses to match for the optional line break. Code:

$string = 'this is some template {$code}. nice! 
{$varinnewline}
{if $bla}1{else}2{/if}
';

echo "<pre>";
preg_replace_callback("/\{([^\}]*)\}(\r\n)?/Us", function($matches) {
  print_r($matches);
}, $string);

It produces (among others) this output:

Array
(
    [0] => {$varinnewline}
    [1] => $varinnewline
)

and not this (which it does if I remove the 0-1 match ? at the end of the regex):

Array
(
    [0] => {$varinnewline}

    [1] => $varinnewline
    [2] => 
)

Basically I want a regex that matches the \\r\\n at the end of the line if it is available. (I need that because after transforming the {} into < ?php ?> the new line after the ?> seems to be removed by the php interpreter)

Answer 1

See a post I answered awhile back explaining this.

• How to match \\r and \\n without using [\\r\\n]?

But to answer your question, apart from \\r and \\n PCRE also has another character group matching newlines, you can use a nifty escape sequence for this case which is \\R .

\\R matches a generic newline; that is, anything considered a linebreak sequence by Unicode. This includes all characters matched by \\v (vertical whitespace) and the multi character sequence \\x0D\\x0A .

preg_replace_callback("~\{([^\}]*)\}(\R)?~", function($matches) {
    print_r($matches);
}, $string);

Output

Array
(
    [0] => {$code}
    [1] => $code
)
Array
(
    [0] => {$varinnewline}

    [1] => $varinnewline
    [2] => 

)
Array
(
    [0] => {if $bla}
    [1] => if $bla
)
Array
(
    [0] => {else}
    [1] => else
)
Array
(
    [0] => {/if}

    [1] => /if
    [2] => 

)