extension_loaded — 检查一个扩展是否已经加载
例如：
<?php
if (!extension_loaded('gd')) {
if (!dl('gd.so')) {
exit;
}
}
?>
是否加载 gd 库扩展
Win7->cmd->php -m
[PHP Modules]
bcmath
bz2
calendar
com_dotnet
ctype
curl
date
dom
filter
ftp
gd
hash
iconv
json
libxml
mbstring
mcrypt
mysql
mysqli
odbc
pcre
PDO
pdo_mysql
PDO_ODBC
pdo_sqlite
Reflection
session
SimpleXML
sockets
SPL
SQLite
standard
tokenizer
wddx
xml
xmlreader
xmlwriter
Zend Optimizer
zip
zlib
[Zend Modules]
Zend Extension Manager
Zend Optimizer
D:PhpphpStudyphp52>
(PHP 4, PHP 5)
get_loaded_extensions — 返回所有编译并加载模块名的 array
array get_loaded_extensions ([ bool $zend_extensions = false ] )