ID: 41739 User updated by: trex0003 at umn dot edu Reported By: trex0003 at umn dot edu -Status: Bogus +Status: Open Bug Type: Documentation problem Operating System: CentOS PHP Version: Irrelevant New Comment:
Please explain the comments added to this report and how it was determined to be "bogus". The comments added by [EMAIL PROTECTED] to the bug do nothing more than reiterate the use of a single, double and quadruple backslash. My question is about why a triple backslash is necessary in this instance. The case of four backslashes in PHP makes sense -- the first and third backslashes escape the second and fourth. But when you have three backslashes in a row, doesn't the third backslash act as an escape character to whatever follows? In my example of: $needle = "/(?<!\\\)'/"; I would expect that the first backslash would escape the second, and the third would escape the right parenthesis, but that's apparently not what happens, because this particular code WORKS. Previous Comments: ------------------------------------------------------------------------ [2007-08-16 14:21:11] [EMAIL PROTECTED] \ character \\ PCRE representation of this character '\\\\' PHP string to write this representation. ------------------------------------------------------------------------ [2007-06-19 17:34:33] trex0003 at umn dot edu Description: ------------ Documentation of how PCRE regex behaves with escaped backslashes is confusing as written in current documentation: http://php.planetmirror.com/manual/en/reference.pcre.pattern.syntax.php Perhaps this just means an expansion of the note: "Note: Single and double quoted PHP strings have special meaning of backslash. Thus if \ has to be matched with a regular expression \\, then "\\\\" or '\\\\' must be used in PHP code." While trying to use preg_split to break a string at non-escaped string quotes, I tried using a negative lookbehind assertion (see code below). With all other escaped characters in the lookbehind assertion, you only need one backwards slash before the escaped character (e.g., "(?<!\s)" works); but if you want to escape a backslash, you need to escape it twice (e.g., "(?<!\\\)" works but "(?<!\\)" does not). Based on the documentation's statement 'In particular, if you want to match a backslash, you write "\\".' it seems that (?<!\\) should work, and the extra information in the Note is too terse to explain why. Perhaps this is actually a bug, but I can't tell if it's normal behavior that could be clarified more in documentation. The closest I could find for bug reports to this issue is here: http://bugs.php.net/bug.php?id=22315 ...but this only implies the difference in behavior without explaining why. Reproduce code: --------------- $string = "This sentence is not quoted. 'But this one is, and it contains \'escaped quotes\' within!'"; $needle = "/(?<!\\)'/"; $results = preg_split($needle, $string); print_r($results); Expected result: ---------------- Array ( [0] => This sentence is not quoted. [1] => But this one is, and it contains \'escaped quotes\' within! [2] => ) // Adding a third backslash to the $needle gives this result. Actual result: -------------- Warning: preg_split() [function.preg-split]: Compilation failed: missing ) at offset 7 in /data/domains/lawweb3.law.umn.edu/public/php/regex.php on line 16 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=41739&edit=1
