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以前偶尔被人问到, 为什么你(和大部分互联网公司)做Web开发要选择PHP, PHP有什么好处. 简单的回答便是"PHP简单,开发快速".

但是, ASP.NET不简单吗? ASP.NET上手不快吗? Python呢?

有些人用各种PHP框架能快速搭建简单博客的例子来说明PHP的优势, 但这全是狗屎! 实际的业务不可能是博客那么简单.

我认为, PHP的最大优势便是他的数据结构和内置函数, 具体地说便是字符串和数组, 以及字符串和数组的函数.

PHP的字符串既能表示一般文本, 也能表示任意二进制数据, 也就是说, PHP的字符串就是一段内存. PHP的的字符串操作函数囊括了大部分常见和不常见的文本操作: 截取, 查找, 正则, 字符集编码转换...每一个都是一把利器.

PHP的数组是整合了列表和哈希表的数据结构. 由于"树"是最能描述现实世界的数据结构, 而PHP的数组可以(轻松地)表示任意树, 所以, PHP的数组也最能描述现实世界(建模).

如果要用一句话来描述PHP的优势, 我会用这一句:"PHP语言的数据结构和内置函数, 可以几乎直接地描述和处理实际业务. PHP是计算机与现实业务的最直接胶合剂."

query_cache_size, tmp_table_size 这两个选项一定要设置!

# The following options will be passed to all MySQL clients
[client]
#password	= your_password
port		= 3306
socket		= /home/work/mysql/tmp/mysql.sock

# Here follows entries for some specific programs

# The MySQL server
[mysqld]
port		= 3306
bind-address = 127.0.0.1
socket		= /home/work/mysql/tmp/mysql.sock
#skip-locking
max_allowed_packet = 1M
table_open_cache = 16
sort_buffer_size = 8M
read_buffer_size = 512K
read_rnd_buffer_size = 256K
net_buffer_length = 8K
thread_stack = 128K

# Size of the Key Buffer, used to cache index blocks for MyISAM tables.
# Do not set it larger than 30% of your available memory, as some memory
# is also required by the OS to cache rows. Even if you're not using
# MyISAM tables, you should still set it to 8-64M as it will also be
# used for internal temporary disk tables.
key_buffer_size = 8M

# If the temporary file used for fast index creation would be bigger
# than using the key cache by the amount specified here, then prefer the
# key cache method.  This is mainly used to force long character keys in
# large tables to use the slower key cache method to create the index.
myisam_sort_buffer_size = 8M

# Query cache is used to cache SELECT results and later return them
# without actual executing the same query once again. Having the query
# cache enabled may result in significant speed improvements, if your
# have a lot of identical queries and rarely changing tables. See the
# "Qcache_lowmem_prunes" status variable to check if the current value
# is high enough for your load.
# Note: In case your tables change very often or if your queries are
# textually different every time, the query cache may result in a
# slowdown instead of a performance improvement.
query_cache_size=16M

# Maximum size for internal (in-memory) temporary tables. If a table
# grows larger than this value, it is automatically converted to disk
# based table This limitation is for a single table. There can be many
# of them.
tmp_table_size=16M


# Don't listen on a TCP/IP port at all. This can be a security enhancement,
# if all processes that need to connect to mysqld run on the same host.
# All interaction with mysqld must be made via Unix sockets or named pipes.
# Note that using this option without enabling named pipes on Windows
# (using the "enable-named-pipe" option) will render mysqld useless!
# 
skip-networking
server-id	= 1

# Uncomment the following if you want to log updates
#log-bin=mysql-bin

# binary logging format - mixed recommended
#binlog_format=mixed

# Uncomment the following if you are using InnoDB tables
#default_storage_engine=InnoDB

innodb_data_home_dir = /home/work/mysql/var/
innodb_data_file_path = ibdata1:10M:autoextend
innodb_log_group_home_dir = /home/work/mysql/var/
# You can set .._buffer_pool_size up to 50 - 80 %
# of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 32M
innodb_additional_mem_pool_size = 4M
# Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 10M
innodb_log_buffer_size = 16M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50

[mysqldump]
quick
max_allowed_packet = 16M

[mysql]
no-auto-rehash
# Remove the next comment character if you are not familiar with SQL
#safe-updates

[myisamchk]
key_buffer_size = 8M
sort_buffer_size = 8M

[mysqlhotcopy]
interactive-timeout

网站如果禁止非浏览器访问, 一般主要还是防止自动 Spam, 主要是:

• 防止网站被机器人恶意抓取
• 防止网站被机器人恶意提交

判断恶意请求(程序和软件直接发送 HTTP 请求)的方法有很多, 比如同 IP 请求频率是. 但一旦判定某个请求为异常行为之后, 并不适合直接关闭该连接, 或者返回出错页. 因为绝大多数的判定方法都无法做到很高的正确率, 其主要原来就是缺少"交互性". "交互性"是判断人和机器的主要因素.

这里判断一种利用交互性来判别是否浏览器正常访问的方法:

1. 当初步判定请求为异常时, 给该请求返回一个动态令牌, 要求对方在下次重新带着该令牌来访问原先请求的资源;
2. 如何告知用户进行这个行为, 根据交互性的强弱依次为:
   1. 设置 Cookie
   2. 通过 JavaScript 脚本的执行(设置 Cookie, 生成带令牌的链接并访问)
   3. 显示网页表单, 要求用户进行点击和输入等操作(单纯的无输入表单, 图片验证码, 声音验证码)
3. 第一种设置 Cookie 太过于简单, 因为一般的机器人都能执行该行为. 第二种 JavaScript 脚本的方式, 其实已经能阻挡大部分机器人. 第三种是非常好的识别那漏掉的一小撮高级机器人, 但同时也可能影响正常用户体验.

重用一个CURL句柄时, 发现curl_setopt($ch, CURLOPT_HTTPGET, TRUE) 不起作用. 期望在调用这条语句之后发起请求, 应该发送的是GET, 但看服务器log, 却使用了和前一次请求相同的HTTP方法.

PHP脚本:

<?php
$url = 'http://www.ideawu.net/';

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_exec($ch);

curl_setopt($ch, CURLOPT_HTTPGET, true); // 错误! BUG
curl_exec($ch);

curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET"); // 正确
curl_exec($ch);
?>

web server log:

124.127.130.50 "2011-10-12 18:55:09" "POST / HTTP/1.1" 200 3516 "-" www.ideawu.net
124.127.130.50 "2011-10-12 18:55:09" "POST / HTTP/1.1" 200 3516 "-" www.ideawu.net
124.127.130.50 "2011-10-12 18:55:09" "GET / HTTP/1.1" 200 3516 "-" www.ideawu.net

这个BUG目前还没找到相关的资料.

补充: 不仅仅是CURLOPT_HTTPGET, CURLOPT_POST也有同样的问题. 所以, 结论是: 只有CURLOPT_CUSTOMREQUEST才是正确的方法.

你可能会觉得PHP中将浮点数(float)转成字符串非常简单, 但是, 常用的方法隐藏着严重的bug. 因为, PHP在处理浮点数时有非常不合理的做法, 会有精度丢失. 经研究, 其实是PHP在显示浮点数时的问题, 也可以说是BUG. PHP内置的echo, var_dump, json_encode, 字符串拼接等函数(指令)在显示浮点数时都有问题, 导致精度丢失.

<?php
$a = 1315537636.338467;
printf("%f", $a); echo "\n";
echo $a . "\n";
echo $a; echo "\n";

结果

1315537636.338467
1315537636.3385
1315537636.3385

也就是说, 用PHP最顺手的方法将浮点数转成字符串或者显示是不行的, 必须使用printf/sprintf将浮点数转成字符串.

虽然用vhost可以支持子域名, 但不方便.

RewriteCond $1 !^bbs/
RewriteCond %{HTTP_HOST} bbs.example.com
RewriteRule (.*) /bbs/$1 [L]

RewriteCond $1 !^bbs/ 避免内部无限redirect.

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