ID: 10666
User Update by: [EMAIL PROTECTED]
Status: Open
Bug Type: PCRE related
Description: preg_replace 'e' modifier
Also, as a merely informational aside, PHP's use of $1 is in this instance actually
incompatible with Perl. Perl, in a s///e expression, treats $n as a variable rather
than expanding it in-place.
Hence my preference. :-)
Previous Comments:
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[2001-05-04 13:55:39] [EMAIL PROTECTED]
Okay. Then I have a problem with how backslash escaping is inconsistently applied
when using \1 and $1.
Specifically, consider the following:
function f($x) { print $x; }
$s = "a' \ "b";
$s = preg_replace('/a(.*)b/e', 'f("$1")', $s, -1);
The single quote is escaped; I'd rather it weren't but that's okay. But the backslash
itself isn't escaped! This prevents me from running stripslashes() on the match,
since I can't guarantee that every backslash has been properly escaped.
Worse, the following will actually fail:
function f($x) { print $x; }
$s = "a' " \b";
$s = preg_replace('/a(.*)b/e', 'f("$1")', $s, -1);
Since the final backslash hasn't been escaped, it actually slurps up the second
double-quote in 'f("$1")'!
I'd like to see either of the following:
1. $1 treated as a "real" variable, rather than a string
substitution. This is convenient, since it saves me
having to call stripslashes().
2. Backslash escapes consistently applied in backrefs.
Specifically, escape existing backslashes in the match.
Presently, I can't perform a stripslashes() -- and in
some cases, as indicated above, it fails altogether!
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[2001-05-04 13:02:59] [EMAIL PROTECTED]
$n notation was introduced to be similar to Perl. It is exactly equivalent to \n.
You can't simply use f($1) in the evaluation string because $1 is replaced with the
matched contents and after replacement it becomes, in your example, f(abc def), which
is not valid PHP code. So you have to use f("$1") or f('$1').
The fact that it backslash-escapes single and double quotes in matches before
substituting $1 is a feature, not a bug, otherwise you'd have a really hard time
figuring out which quotes go where when using evaluation strings.
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[2001-05-04 11:27:54] [EMAIL PROTECTED]
Formerly, preg_replace's "e" modifier inserted extraneous backslashes in
backreferences of "\1" or '\1' form.
Ostensibly, the $1 backreference form was added to fix this. However, the following
code fails:
function f($x) { return 'yo'; }
$s = "xyzabc def123";
$s = preg_replace('/(abc def)/e', 'f($1)', $s, -1);
It seems to be trying to evaluate $1 as code, rather than as a variable containing the
contents "abc def".
This is borne out by the fact that the following succeeds:
$s = preg_replace('/(abc def)/e', 'f("$1")', $s, -1);
But "$1" and '$1' are no better than "\1" and '\1', since it still inserts extraneous
backslashes before single quotes or double quotes (respectively)!!!
I was sincerely hoping that PHP 4.04 and 4.05 would fix this oversight, since my web
application depends on it. I'm keeping my fingers crossed that it's just me doing
something wrong, though I doubt it...
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Full Bug description available at: http://bugs.php.net/?id=10666
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