mysql Unable to load dynamic library

mysql 起不来
查看 error.log 错误信息如下
PHP startup: Unable to load dynamic library './php_mysql.dll 找不到指定的模块。

解决如下：
1、extension_dir要设置正确。
2、把所依赖的dll拷贝到%windir%\system32
3、或者将PHP的安装目录添加到%path%中.

引起原因:
库依赖,找不到对应的库.

库依赖
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).