Q: php_mysql.dll为例，php_mysql依赖libmysql.dll，文件都在extension_dir的路径中，为什么apache就是说找不到？
A: 由于PHP5改变文件的位置了，而多数是用.zip发布，所以造成无法复制很多dll到正确路径中去,造成httpd无法调用这些backend dll。
   解决的办法有两个：
1 将这些依赖的dll拷贝到％windir％\system32下
2 或者将PHP5的安装目录添加到%PATH%中。(有人说能行，我这就没成功过)

Q: 那些dll调用其它的dll,需要被复制到%system32%,或者%path%中去？
A: Php5官方网站有个列表，好早以前我找过，这里做个list

php_curl.dll CURL, Client URL library functions Requires:   libeay32.dll, ssleay32.dll (bundled)
php_domxml.dll DOM XML functions PHP <= 4.2.0 requires: libxml2.dll
   (bundled) PHP >= 4.3.0 requires: iconv.dll (bundled)
php_fdf.dll FDF: Forms Data Format functions. Requires: fdftk.dll
gnu_gettext.dll (bundled), PHP >= 4.2.3 requires libintl-1.dll,
php_iconv.dll ICONV characterset conversion Requires: iconv-1.3.dll
php_ingres.dll Ingres II functions Requires: Ingres II libraries
php_interbase.dll InterBase functions Requires: gds32.dll (bundled)
php_java.dll Java functions PHP <= 4.0.6 requires: jvm.dll (bundled)
php_ldap.dll LDAP functions PHP <= 4.2.0 requires libsasl.dll(bundled),
     PHP >= 4.3.0 requires libeay32.dll,ssleay32.dll (bundled)
php_mcrypt.dll Mcrypt Encryption functions Requires: libmcrypt.dll
php_mhash.dll Mhash functions PHP >= 4.3.0 requires: libmhash.dll   (bundled)
php_mcrypt.dll Mcrypt Encryption functions Requires: libmcrypt.dll
php_mhash.dll Mhash functions PHP >= 4.3.0 requires: libmhash.dll   (bundled)
php_msql.dll mSQL functions Requires: msql.dll (bundled)
php_mssql.dll MSSQL functions Requires: ntwdblib.dll (bundled)
php_mysql.dll MySQL functions PHP >= 5.0.0, requires libmysql.dll   (bundled)
php_mysqli.dll MySQLi functions PHP >= 5.0.0, requires libmysqli.dll   (bundled)
php_oci8.dll Oracle 8 functions Requires: Oracle 8.1+ client libraries
php_openssl.dll OpenSSL functions Requires: libeay32.dll (bundled)
php_oracle.dll Oracle functions Requires: Oracle 7 client libraries
php_sybase_ct.dll Sybase functions Requires: Sybase client libraries
php_xmlrpc.dll XML-RPC functions PHP >= 4.2.1 requires: iconv.dll   (bundled)
php_xslt.dll XSLT functions PHP <= 4.2.0 requires sablot.dll,  expat.dll (bundled).
        PHP >= 4.2.1 requires sablot.dll, expat.dll,  iconv.dll (bundled).