楼上两位大侠已经说得很清楚了: function_exists()function_exists (PHP 4, PHP 5)function_exists — Return TRUE if the given function has been defined说明 bool function_exists ( string $function_name ) Checks the list of defined functions, both built-in (internal) and user-defined, for function_name. 参数function_name The function name, as a string. 返回值 Returns TRUE if function_name exists and is a function, FALSE otherwise. Note: This function will return FALSE for constructs, such as include_once() and echo(). 范例Example #1 function_exists() example<?php if (function_exists('imap_open')) { echo "IMAP functions are available.<br />\n"; } else { echo "IMAP functions are not available.<br />\n"; } ?> get_loaded_extensions ()get_loaded_extensions (PHP 4, PHP 5)get_loaded_extensions — Returns an array with the names of all modules compiled and loaded说明 array get_loaded_extensions ([ bool $zend_extensions = false ] ) This function returns the names of all the modules compiled and loaded in the PHP interpreter. 参数zend_extensions Only return Zend extensions, if not then regular extensions, like mysqli are listed. Defaults to FALSE (return regular extensions). 返回值 Returns an indexed array of all the modules names. 更新日志 版本 说明 5.2.4 The optional zend_extensions parameter was added 范例Example #1 get_loaded_extensions() Example<?php print_r(get_loaded_extensions()); ?> 以上例程的输出类似于:Array ( [0] => xml [1] => wddx [2] => standard [3] => session [4] => posix [5] => pgsql [6] => pcre [7] => gd [8] => ftp [9] => db [10] => calendar [11] => bcmath )
你都不查手册的吗?extension_loaded (PHP 3 >= 3.0.10, PHP 4, PHP 5)extension_loaded -- Find out whether an extension is loaded Description bool extension_loaded ( string name ) Returns TRUE if the extension identified by name is loaded, FALSE otherwise. 例子 1. extension_loaded() example<?php if (!extension_loaded('gd')) { if (!dl('gd.so')) { exit; } } ?>
#2.function_exists //用来判断扩展库里的某个方法存不存在
function_exists()function_exists
(PHP 4, PHP 5)function_exists — Return TRUE if the given function has been defined说明
bool function_exists ( string $function_name )
Checks the list of defined functions, both built-in (internal) and user-defined, for function_name. 参数function_name
The function name, as a string.
返回值
Returns TRUE if function_name exists and is a function, FALSE otherwise. Note: This function will return FALSE for constructs, such as include_once() and echo().
范例Example #1 function_exists() example<?php
if (function_exists('imap_open')) {
echo "IMAP functions are available.<br />\n";
} else {
echo "IMAP functions are not available.<br />\n";
}
?> get_loaded_extensions ()get_loaded_extensions
(PHP 4, PHP 5)get_loaded_extensions — Returns an array with the names of all modules compiled and loaded说明
array get_loaded_extensions ([ bool $zend_extensions = false ] )
This function returns the names of all the modules compiled and loaded in the PHP interpreter. 参数zend_extensions
Only return Zend extensions, if not then regular extensions, like mysqli are listed. Defaults to FALSE (return regular extensions).
返回值
Returns an indexed array of all the modules names. 更新日志
版本 说明
5.2.4 The optional zend_extensions parameter was added
范例Example #1 get_loaded_extensions() Example<?php
print_r(get_loaded_extensions());
?>
以上例程的输出类似于:Array
(
[0] => xml
[1] => wddx
[2] => standard
[3] => session
[4] => posix
[5] => pgsql
[6] => pcre
[7] => gd
[8] => ftp
[9] => db
[10] => calendar
[11] => bcmath
)
(PHP 3 >= 3.0.10, PHP 4, PHP 5)extension_loaded -- Find out whether an extension is loaded
Description
bool extension_loaded ( string name )
Returns TRUE if the extension identified by name is loaded, FALSE otherwise. 例子 1. extension_loaded() example<?php
if (!extension_loaded('gd')) {
if (!dl('gd.so')) {
exit;
}
}
?>
函数搞定,这个是我这边打印出来的:Array
(
[0] => bcmath
[1] => calendar
[2] => com_dotnet
[3] => ctype
[4] => session
[5] => filter
[6] => ftp
[7] => hash
[8] => iconv
[9] => json
[10] => odbc
[11] => pcre
[12] => Reflection
[13] => date
[14] => libxml
[15] => standard
[16] => tokenizer
[17] => zlib
[18] => SimpleXML
[19] => dom
[20] => SPL
[21] => wddx
[22] => xml
[23] => xmlreader
[24] => xmlwriter
[25] => apache2handler
[26] => gd
[27] => mbstring
[28] => mssql
[29] => mysql
[30] => mysqli
[31] => PDO
[32] => pdo_mysql
[33] => SQLite
[34] => Zend Optimizer
)