mod_rewrite是apache一個(gè)允許服務(wù)器端對請求url做修改的模塊。入端url將和一系列的rule來比對。這些rule包含一個(gè)正則表達(dá)式以便檢測每個(gè)特別的模式。如果在url中檢測到該模式，并且適當(dāng)?shù)念A(yù)設(shè)條件滿足，name該模式將被一個(gè)預(yù)設(shè)的字符串或者行為所替換。

這個(gè)過程持續(xù)進(jìn)行直到?jīng)]有任何未處理的規(guī)則或者該過程被顯式地停止。

這可以用三點(diǎn)來總結(jié)：

• 有一系列的順序處理的規(guī)則rule集
• 如果有一條規(guī)則被匹配，將同時(shí)檢查該規(guī)則對應(yīng)的條件是否滿足
• 如果一切處理結(jié)果都是go，那么將執(zhí)行一條替換或者其他動(dòng)作

有一些比較明顯的好處，但是也有一些并不是很明顯：

mod_rewrite非常普遍地被用于轉(zhuǎn)換丑陋的，難以明義的URL，形成所謂"友好或干凈的url"。

另一方面，這些轉(zhuǎn)換后的url將會(huì)是搜索引擎友好的

/s{2,}　　2個(gè)以上的空格

/|　　　　backward referrence

//　　　　matches a '/'

/b　　　　Word boundary position,比如whitespace或者字符串的開始或者結(jié)束

/B　　　　Not a word boundary position

(?=ABC)　　positive lookahead. Matches a group after your main exPRession without including it in the result

(?!ABC)　　Negative lookahead.Specifies a group that can not match after your main expression(ie. if it matches, the result is discarded)

(?<=ABC) Positive lookbehind. Matches a group before your main expression without including it in the result.

(?<!ABC)　　Negative lookbehind.Specifies a group that can not match before your main expression(ie.if it matches, the result is discarded)

*?　　　　:match zero or more of the preceeding token. This is a lazy match, and will match as few characters as possible before satisfying the next token

+?　　　　:match one or more of the preceeding token. This is a lazy match, and will match as few characters as possible before satisfying the next token

{5}　　　 :matches exactly 5 of the preceeding token;

{2,5}　　: matches 2 to 5 of the preceding token. Greedy match;

{2,5}?　　matches 2 to 5 of the preceding token. lazy match;

(ABC)　　groups multiple tokens together. This allows you to apply quantifiers to the fall group. Creates a capture group roll over a match highlight to see the capture group result

(?:ABC)　　groups multiple tokens without creating capture group;

$$　　　　escaped $ symbol　　　　　　 $`: insert the portion of the string that precedes the match

$&:　　　　inserts the matched substring $' : insert the portion of the string that follows the match[$1]:　　　　inserts the result of the first capture group

m　　　　　　multiline

i　　　　　　　ignore case

"S"　　　　　　match any character, except for line breaks if dotall is false

"g"　　　　search globally

?　　　　zero or one

/　　　　escape

/.　　//　　/+　　/*　　/?　　/^　　/$　　/[　　/]　　/(　　/)　　/{　　/}　　//　　/'　　/#

[ABC]　　Any single character in ABC set

+　　　　one or more

*　　　　zero or more

|　　or matches the full before or after '|'　　　　　　(https?|ftp)://

^　　　　matches the beginning of the string　　　　

$　　　　matches the end of the string

$1　　　　refer to a match

$2　　　　refer to another match

?:　　within parenthesis to not capture (^.+(?:jpg|png|gif)$)

[^ABC]　　　Any single character not in the set

[a-z]　　　　any single character in the a-z range

[^b-e]　　　　any single character that is not in range b-e

[0-9]

[/w'-]　　any world characater, single quote or -

/t　　/r/n　　tab

/xFF　　　　specifying a character by its hexdecimal index

/xA9 => copyright symbol