The Doctrine project does not explicitly require a specific version of MySQL, because database abstraction and access level is a thin shell around PDO
So the question is: What is required PDO_MYSQL?
From the PDO_MYSQL docs :
PDO_MYSQL is a driver that implements the PHP Data Objects (PDO) interface to provide access from PHP to MySQL 3.x, 4.x and 5.x databases.
PDO_MYSQL (and by extension Doctrine2) can work with versions of MySQL already in 3.x.
But, note that on the same page he mentions:
since PHP 5.4. MySQL client libraries 4.1 and below are no longer supported.
So, if you are using PHP 5.4+, you need to use MySQL 5.0 to use Doctrine2.
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