Description:
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PHP's MySQL PDO driver can't set collations without an init command, although the "charset=" parameter was introduced in PHP 5.3.6 to enable specifying the character set without the need for an init command. (See https://secure.php.net/manual/en/ref.pdo-mysql.connection.php)

See Anthony Rutledge's answer over at https://stackoverflow.com/questions/25807202/how-to-specify-collation-with-pdo-without-set-names/32553447#32553447 for further details regarding this issue.

Test script:
---------------
<?php
$db = new PDO('mysql:host=HostnameOrIpHere;dbname=DbNameHere;charset=utf8',
              'DbUserHere',
              'DbPasswordHere',
              array(PDO::ATTR_EMULATE_PREPARES => false,
                    PDO::ATTR_ERRMODE          => PDO::ERRMODE_EXCEPTION));
echo $db->query("SELECT COLLATION('foo')")->fetch(PDO::FETCH_NUM)[0];
?>

Expected result:
----------------
PDO's MySQL driver should allow for setting the collation explicitly, i. e. via proper value for the "charset" parameter, e. g. changing test script's 2nd line to

$db = new PDO('mysql:host=HostnameOrIpHere;dbname=DbNameHere;charset=utf8_unicode_ci',

or by adding another parameter, e. g. "collation", for this should result in this output: utf8_general_ci

But since MySQL always uses "charset_collation" (optionally combined with "_ci" for case-insensitive comparison), I suggest only modifying which would be backwards compatible: utf8 -> works as before, utf8_unicode[_ci] -> utf8 for charset and unicode[_ci] for collation, if present.

Actual result:
--------------
Test script's expected output, utf8_general_ci

Workaround: using PDO::MYSQL_ATTR_INIT_COMMAND with a value of "SET NAMES 'utf8' COLLATE 'utf8_unicode_ci'" (including quotes) as a third array element in the test script above, results in utf8_unicode_ci - but this should be considered as a temporary workaround as PHP introduced the "charset=" parameter to eliminate the need for setting it via init command.