注意：我知道以下问题已经问了很多遍了。我尝试在线跟踪解决方案，但是尝试跟踪解决方案并没有成功。因此，我希望有人可以针对我的具体情况逐步指导我。
我一直在尝试创建链接到数据库的网页。当我使用sqlsrv_connect（）函数时，该网页向我显示一条错误消息，内容为Call to undefined function sqlsrv_connect()。我查看了PHP错误日志，上面写着
[30-Nov-2019 18:19:39 UTC] PHP Warning: PHP Startup: Unable to load dynamic library 'oci8_12c' (tried: ext\oci8_12c (The specified module could not be found.), ext\php_oci8_12c.dll (The specified module could not be found.)) in Unknown on line 0
[30-Nov-2019 18:19:39 UTC] PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_firebird' (tried: ext\pdo_firebird (The specified module could not be found.), ext\php_pdo_firebird.dll (The specified module could not be found.)) in Unknown on line 0
[30-Nov-2019 18:19:39 UTC] PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_oci' (tried: ext\pdo_oci (The specified module could not be found.), ext\php_pdo_oci.dll (The specified module could not be found.)) in Unknown on line 0
在php.ini文件中，我未注释以下内容：
extension=oci8_12c ; Use with Oracle Database 12c Instant Client
extension=pdo_firebird
extension=pdo_oci
以上所有扩展dll文件都存在于我的php / ext文件夹中。
为什么会收到此警告以及如何解决？