Can't tell for the 17.0.0.1062 GA release, however, for later builds, the omition of the PHP drivers is an expected behaviour change - from the readme of newer EBFs - the mentioned web page being the one Nick has pointed to, I'd assume:) -:

================(Build #1187  - Engineering Case #785851)================

SQL Anywhere installations no longer include PHP drivers. They are now posted 
to a web page, but the versions posted only include the .0 release of each 
major/minor version.

The PHP external environment attempts to load the external environment DLL 
that matches the current phpversion(), which includes the release number.  
Unless the release number is 0, or an appropriate driver was previously installed, 
the correct driver will not be found and the PHP external environment will 
fail to start.

This has been fixed.  If a DLL with the full version number is available, 
it will be used.  Otherwise the DLL with the .0 release number will be used.  
e.g. PHP 5.6.5 would use the 5.6.0 DLL.

SQLA 12.0.1 and 16.0.0 should continue to work as before, but the fix was 
included to allow for possible future changes.

Workarounds include (one of):
- rename the SQLA PHP modules to a name that will be found
- set up a php.ini file containing the “extension” setting that will load 
the SQLA PHP modules
- compile the PHP drivers in the SDK directory to match your PHP installation