Description:
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PDO currently supports the following directives:
pdo_mysql.default_socket
pdo_mysql.debug

PDO constructor ignores any of mysql[i].default_* directives.

Because it's both a missing feature and lacks consistency, supporting default_user, default_password (and why not default_host and default_port) would be great.

Defaulting to the corresponding mysql.* or mysqli.* directives according to the select DB driver may also be an option (while adding a bit more magic).

Stated that, as for mysql[i]_connect, these values are taken into account only if $user and $password are either NULL or omitted.


Test script:
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// php_value	pdo_mysql.default_user	"test" // in httpd configuration
// or ini_set('pdo_mysql.default_user', 'test')
new PDO('mysql:host=localhost;dbname=test'); // $user and $password parameters omitted
// success