/**************by garcon1986*******************/

PEAR （PHP Extension and Application Repository）PHP擴充套件與應用程式庫。

PEAR是“一個可重用PHP元件的框架和釋出系統”。PEAR可以下載、安裝、升級及刪除PHP指令碼。 使用PEAR包的時候，不必為了指令碼的位置或者怎麼找到它們而擔心，擴充套件命令列介面（CLI）也很容易使用。
PEAR是一個由社群推動的PHP專案，官方釋出的PHP中就包含了PEAR。

PECL (PHP 擴充套件庫)的全稱是 The PHP Extension Community Library ，是一個開放的並通過PEAR打包格式來打包安裝的PHP 擴充套件庫倉庫。通過PEAR 的Package Manager可以對 PECL 模組進行下載和安裝。

PEAR和PECL的區別：

Pear：是PHP的擴充套件程式碼包，所有的擴充套件均以PHP程式碼的形式出現，功能強大，安裝簡單，甚至可以改改就用。使用的時候，要在程式碼中進行Include才能夠使用。


Pecl：是PHP的標準擴充套件，可以補充實際開發中所需的功能，所有的擴充套件都需要安裝，在Windows下面以Dll的形式出現，在linux下面，需要單獨進行編譯，它的表現形式為根據PHP官方的標準用C語言寫成，儘管原始碼開放但是一般人無法隨意更改原始碼。

最直接的表述：Pear是PHP的上層擴充套件，Pecl是PHP的底層擴充套件。

這兩種方法其實都是為特定的應用提供現成的函式或者類，本質上來說都是一樣的。

正則表示式 ：

PCRE ：PERL相容正則表示式函式（perl compatible regular expression）

函式：

• preg_filter — Perform a regular expression search and replace
• preg_grep — Return array entries that match the pattern
• preg_last_error — Returns the error code of the last PCRE regex execution
• preg_match_all — Perform a global regular expression match
• preg_match — Perform a regular expression match
• preg_quote — Quote regular expression characters
• preg_replace_callback — Perform a regular expression search and replace using a callback
• preg_replace — Perform a regular expression search and replace
• preg_split — Split string by a regular expression

POSIX ：

函式：

• posix_access — Determine accessibility of a file
• posix_ctermid — Get path name of controlling terminal
• posix_errno — Alias of posix_get_last_error
• posix_get_last_error — Retrieve the error number set by the last posix function that failed
• posix_getcwd — Pathname of current directory
• posix_getegid — Return the effective group ID of the current process
• posix_geteuid — Return the effective user ID of the current process
• posix_getgid — Return the real group ID of the current process
• posix_getgrgid — Return info about a group by group id
• posix_getgrnam — Return info about a group by name
• posix_getgroups — Return the group set of the current process
• posix_getpgid — Get process group id for job control
• posix_getpgrp — Return the current process group identifier
• posix_getpid — Return the current process identifier
• posix_getppid — Return the parent process identifier
• posix_getpwnam — Return info about a user by username
• posix_getpwuid — Return info about a user by user id
• posix_getrlimit — Return info about system resource limits
• posix_getsid — Get the current sid of the process
• posix_getuid — Return the real user ID of the current process
• posix_initgroups — Calculate the group access list
• posix_isatty — Determine if a file descriptor is an interactive terminal
• posix_kill — Send a signal to a process
• posix_mkfifo — Create a fifo special file (a named pipe)
• posix_mknod — Create a special or ordinary file (POSIX.1)
• posix_setegid — Set the effective GID of the current process
• posix_seteuid — Set the effective UID of the current process
• posix_setgid — Set the GID of the current process
• posix_setpgid — Set process group id for job control
• posix_setsid — Make the current process a session leader
• posix_setuid — Set the UID of the current process
• posix_strerror — Retrieve the system error message associated with the given errno
• posix_ttyname — Determine terminal device name

PCRE比POSIX更強大。