MySQL Enterprise Connector/PHP Plugin for php 5.4
Now a little update:

I tried mysqlenterprise.so for php 5.4, 5.5 and 5.6 and i'm sure it won't work cause it's a compatibility issue.

In PHP Plugin Pack 3.0.22 there's only mysql-enterprise-plugin-1.0.1-php5.3 and unfortunately it works only on php 5.3. It caused by the change of php_body_write to php_output_write on PHPAPI main/output.c after 5.4 release. I checked if there's a new extension but can not find anything.

Only solution seems to open a support ticket.



As shown in documentation you need to load your mysqlnd before mysqlenterprise.so. Mostly this error is about wrong configuration or choosing wrong version for extensions. 

Did you compile your php enabled with mysqlnd or installed mysqlnd extension? 

First check your php configuration on command line with php -i for controlling your extensions loaded successfully.
You can read more clean you grep result with mysql and check your extension list with grep -Hrv ";" /etc/php.d/ | grep -i "extension="

/etc/php.d directory can be different in different installations.

If you can't see your extensions details, check your php configuration ini files under extension folderand make sure you have mysqlnd.ini. For mysql enterprise ini file, you can create one mysqlzz_enterprise.ini or just add it in mysqlnd.ini file.

If this not solve your problem, try to uninstall php and make sure you installed mysqlnd, then add your extension to your ini file, check your extension ini files as in documentation tells. 

Example configure options for php source build:

./configure --with-pdo-mysql=mysqlnd --with-mysql=mysqlnd