原正則的出現(xiàn)是為了實現(xiàn)apache上傳目錄無執(zhí)行權(quán)限,不過大家知道在 windows下對于文件名是不區(qū)分大小寫的,但在*unx下就不同了,其中st0p.php和st0p.Php是兩個不同的文件,所以此正則(?i:.php)出現(xiàn)

kindle說是參考http://perldoc.perl.org/perlre.html#Extended-Patterns的內(nèi)容進行寫的,具體的內(nèi)容大家自己看,我們說一下關(guān)于此表達式的部分..

我們找到?:相關(guān)的部分,其用法有兩種(?:pattern)和(?imsx-imsx:pattern)
我們需要用的是后者,前者的話是沒法區(qū)分大小寫的.而后者的用法就是(?標志修飾符:格式)
其中原文中有一句話是Any letters between ? and : act as flags modifiers as with (?imsx-imsx).
這句話就說明了imsx-imsx的作用,標志修飾符
我們看一下剛才出現(xiàn)的正則(?i:.php)
?的作用是在默認的貪婪模式下盡可能多的匹配所搜索的字符串,當該字符緊跟在任何一個其他限制符 (*, +, ?, {n}, {n,}, {n,m}) 后面時，匹配模式是非貪婪的。非貪婪模式盡可能少的匹配所搜索的字符串,例如，對于字符串 “oooo”，’o+?’ 將匹配單個 “o”，而 ‘o+’ 將匹配所有 ‘o’。

其中i的作用為忽略大小寫
.php就是我們需要匹配的部分,由于?和i的作用,那我們的正則就會在不區(qū)分大小寫的情況下盡可能多的匹配所搜索的字符串,這樣就達到了我們禁用所有.php后綴文件的訪問了

當然還有別的參數(shù),更多的內(nèi)容大家參考一下http://perldoc.perl.org/perlre.html#Extended-Patterns

m
Treat string as multiple lines. That is, change “^” and “$” from matching the start or end of the string to matching the start or end of any line anywhere within the string.

s
Treat string as single line. That is, change “.” to match any character whatsoever, even a newline, which normally it would not match.
Used together, as /ms, they let the “.” match any character whatsoever, while still allowing “^” and “$” to match, respectively, just after and just before newlines within the string.

i
Do case-insensitive pattern matching.
If use locale is in effect, the case map is taken from the current locale. See perllocale.

x
Extend your pattern’s legibility by permitting whitespace and comments.

p
Preserve the string matched such that ${^PREMATCH}, ${^MATCH}, and ${^POSTMATCH} are available for use after matching.

g and c
Global matching, and keep the Current position after failed matching. Unlike i, m, s and x, these two flags affect the way the regex is used rather than the regex itself. See “Using regular expressions in Perl” in perlretut for further explanation of the g and c modifiers.

其中:應(yīng)該只是一個分隔符吧,不知道還有沒有別的作用,如果哪個大牛知道,請告訴我.

.php就是我們要匹配的部分了,從上面的圖我們..