If I may - I posted this on Git. I had this VERY same issue. There is a PATH which needs to be added in environment variables for the PHP LDAP extension to work. First though you need to ensure you're editing the right PATH variable. Most of the install documents for PHP LDAP say that you need to edit the "global" PATH variable. The issue is that MY install of PHP and apache did not use the "global" path variable but rather used the system path variable.
The below needs to be added to the end of the right PATH variable:
;<you path to PHP>
You can verify which PATH variable is being used by looking at the entries in the PHP INFO file which @ntozier posted to code to create above.
Hope this helps and respond here if you have issues. Happy to help.
Rich
