Description
bool 
extension_loaded ( string name)
     Returns TRUE if the extension identified by name
     is loaded, FALSE otherwise.
    
     
| 例子 1. extension_loaded() example | 
<?phpif (!extension_loaded('gd')) {
 if (!dl('gd.so')) {
 exit;
 }
 }
 ?>
 | 
 | 
    
     You can see the names of various extensions by using
     phpinfo() or if you're using the
     CGI or CLI version of
     PHP you can use the -m switch to
     list all available extensions:
     
| $ php -m
[PHP Modules]
xml
tokenizer
standard
sockets
session
posix
pcre
overload
mysql
mbstring
ctype
[Zend Modules] | 
    注: 
      extension_loaded() uses the internal extension name
      to test whether a certain extension is available or not. Most internal
      extension names are written in lower case but there may be extension
      available which also use uppercase letters. Be warned that this
      function compares case sensitive !
     
     See also 
     get_loaded_extensions(),
     get_extension_funcs(),
     phpinfo(), and
     dl().