PHP中文网

从静态到动态
说明:
如何无缝转换静态页面foo.html为动态的foo.cgi，而不为浏览器/用户所察觉。

方案:
只须重写此URL为CGI-script，以强制为可以作为CGI-script运行的正确的MIME类型。如此，对/~quux/foo.html的请求其实会执行/~quux/foo.cgi。

代码:
RewriteEngine on
RewriteBase /~quux/
RewriteRule ^foo\.html$ foo.cgi [T=application/x-httpd-cgi]
空闲时间内的内容协商
说明:
这是一个很难解的功能：动态生成的静态页面，即，它应该作为静态页面发送(从文件系统中读出，然后直接发出去)，但是如果它丢失了，则由服务器动态生成。如此，可以静态地提供CGI生成的页面，除非有人(或者是一个cronjob)删除了这些静态页面，而且其内容可以得到更新。

方案:
以下规则集实现这个功能：
代码:
RewriteCond %{REQUEST_FILENAME} !-s
RewriteRule ^page\.html$ page.cgi [T=application/x-httpd-cgi,L]
这样，如果page.html不存在或者文件大小为null，则对page.html的请求会导致page.cgi的运行。其中奥妙在于，page.cgi是一个将输出写入page.html的(同时也写入STDOUT)的常规的CGI脚本，执行完毕，服务器则将page.html的内容发出。如果网管需要强制更新其内容，只须删除page.html即可(通常由一个cronjob完成)。

自动更新的文档
说明:
建立一个复杂的页面，能够在用编辑器写了一个更新的版本时自动在浏览器上得到刷新，这不是很好吗？这可能吗？

方案:
这是可行的! 这需要综合利用MIME多成分、网站服务器的NPH和mod_rewrite的URL操控特性。首先，建立一个新的URL特性：对在文件系统中更新时需要刷新的所有URL加上:refresh。

代码:
RewriteRule ^(/[uge]/[^/]+/?.*):refresh /internal/cgi/apache/nph-refresh?f=$1
然后，修改URL

代码:
/u/foo/bar/page.html:refresh
以内部地操控此URL

代码:
/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html
接着就是NPH-CGI脚本部分了。虽然，人们常说”left as an exercise to the reader”，我还是给出答案了。

代码:
#!/sw/bin/perl
##
## nph-refresh — NPH/CGI script for auto refreshing pages
## Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
##
$| = 1;

# split the QUERY_STRING variable
@pairs = split(/&/, $ENV{‘QUERY_STRING’});
foreach $pair (@pairs) {
($name, $value) = split(/=/, $pair);
$name =~ tr/A-Z/a-z/;
$name = ‘QS_’ . $name;
$value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack(“C”, hex($1))/eg;
eval “\$name = \”$value\”";
}
$QS_s = 1 if ($QS_s eq ”);
$QS_n = 3600 if ($QS_n eq ”);
if ($QS_f eq ”) {
print “HTTP/1.0 200 OK\n”;
print “Content-type: text/html\n\n”;
print “&b&ERROR&/b&: No file given\n”;
exit(0);
}
if (! -f $QS_f) {
print “HTTP/1.0 200 OK\n”;
print “Content-type: text/html\n\n”;
print “&b&ERROR&/b&: File $QS_f not found\n”;
exit(0);
}

sub print_http_headers_multipart_begin {
print “HTTP/1.0 200 OK\n”;
$bound = “ThisRandomString12345″;
print “Content-type: multipart/x-mixed-replace;boundary=$bound\n”;
&print_http_headers_multipart_next;
}

sub print_http_headers_multipart_next {
print “\n–$bound\n”;
}

sub print_http_headers_multipart_end {
print “\n–$bound–\n”;
}

sub displayhtml {
local($buffer) = @_;
$len = length($buffer);
print “Content-type: text/html\n”;
print “Content-length: $len\n\n”;
print $buffer;
}

sub readfile {
local($file) = @_;
local(*FP, $size, $buffer, $bytes);
($x, $x, $x, $x, $x, $x, $x, $size) = stat($file);
$size = sprintf(“%d”, $size);
open(FP, “&$file”);
$bytes = sysread(FP, $buffer, $size);
close(FP);
return $buffer;
}

$buffer = &readfile($QS_f);
&print_http_headers_multipart_begin;
&displayhtml($buffer);

sub mystat {
local($file) =$_[0];
local($time);

($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file);
return $mtime;
}

$mtimeL = &mystat($QS_f);
$mtime = $mtime;
for ($n = 0; $n & $QS_n; $n++) {
while (1) {
$mtime = &mystat($QS_f);
if ($mtime ne $mtimeL) {
$mtimeL = $mtime;
sleep(2);
$buffer = &readfile($QS_f);
&print_http_headers_multipart_next;
&displayhtml($buffer);
sleep(5);
$mtimeL = &mystat($QS_f);
last;
}
sleep($QS_s);
}
}

&print_http_headers_multipart_end;

exit(0);

##EOF##
大型虚拟主机
说明:
Apache的<VirtualHost>功能很强，在有几十个虚拟主机的情况下运行得很好，但是如果你是ISP，需要提供几百个虚拟主机，那么这就不是一个最佳的选择了。

方案:
为此，需要用代理吞吐(Proxy Throughput)功能(flag [P])映射远程页面甚至整个远程网络区域到自己的名称空间：

代码:
##
## vhost.map
##
www.vhost1.dom:80 /path/to/docroot/vhost1
www.vhost2.dom:80 /path/to/docroot/vhost2
:
www.vhostN.dom:80 /path/to/docroot/vhostN

代码:
##
## httpd.conf
##
:
# use the canonical hostname on redirects, etc.
UseCanonicalName on

:
# add the virtual host in front of the CLF-format
CustomLog /path/to/access_log “%{VHOST}e %h %l %u %t \”%r\” %>s %b”
:

# enable the rewriting engine in the main server
RewriteEngine on

# define two maps: one for fixing the URL and one which defines
# the available virtual hosts with their corresponding
# DocumentRoot.
RewriteMap lowercase int:tolower
RewriteMap vhost txt:/path/to/vhost.map

# Now do the actual virtual host mapping
# via a huge and complicated single rule:
#
# 1. make sure we don’t map for common locations
RewriteCond %{REQUEST_URL} !^/commonurl1/.*
RewriteCond %{REQUEST_URL} !^/commonurl2/.*
:
RewriteCond %{REQUEST_URL} !^/commonurlN/.*
#
# 2. make sure we have a Host header, because
# currently our approach only supports
# virtual hosting through this header
RewriteCond %{HTTP_HOST} !^$
#
# 3. lowercase the hostname
RewriteCond ${lowercase:%{HTTP_HOST}|NONE} ^(.+)$
#
# 4. lookup this hostname in vhost.map and
# remember it only when it is a path
# (and not “NONE” from above)
RewriteCond ${vhost:%1} ^(/.*)$
#
# 5. finally we can map the URL to its docroot location
# and remember the virtual host for logging puposes
RewriteRule ^/(.*)$ %1/$1 [E=VHOST:${lowercase:%{HTTP_HOST}}]
: