I am using PDO for WordPress with PHP 5.1, which should fall within the requirements. However, the installation process breaks in step 2. This probably produces a clear error, but I don't have access to PHP logs on my server.
I tracked the bug down to the use of the function preg_last_error() in file wp-content/pdo/driver_sqlite/pdo_sqlite_driver_create.php. This function was introduced in PHP 5.2. I propose the following patch (taken from PDO version 2.7.0):
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< if (function_exists('preg_last_error')) { // PHP >= 5.2.0
< $this->_errors[] = preg_last_error();
< } else {
< // No way to check for errors in PHP < 5.2
< // Silently ignore errors.
< $this->_errors[] = 0; // PREG_NO_ERROR
< }
---
> $this->_errors[] = preg_last_error();
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< }
---
> }
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