DsnReader.php

<?php

class DsnReader
{
    private $dsn;

    public function __construct($dsn)
    {
        $this->dsn = $dsn;
    }

    public function getDsnValue($element)
    {
        list($value) = explode(';', substr($this->dsn, strpos($this->dsn, $element) + strlen($element) + 1));
        if (false !== strpos($value, '=') || ! $value) {
            throw new \InvalidArgumentException(sprintf(
                'element "%s" not found in the dsn string',
                $element
            ));
        }

        return $value;
    }

    public function getScheme()
    {
        $scheme = strstr($this->dsn, ':', true) . ':';
        if (! $scheme) {
            throw new \InvalidArgumentException(
                'scheme not found in the dsn string'
            );
        }

        return $scheme;
    }

    public function extract()
    {
        $data = [];
        $data['scheme'] = $this->getScheme();

        $lists = explode(';', substr($this->dsn, strlen($data['scheme'])));
        if (empty($lists[1])) {
            throw new \InvalidArgumentException(
                'no dsn element found'
            );
        }

        foreach ($lists as $val) {
            list($element, $value) = explode('=', $val);
            $data[$element] = $value;
        }

        return $data;
    }
}

$dsn = new DsnReader('mysql:dbname=foo;host=localhost;port=3306');
echo $dsn->getDsnValue('dbname') . PHP_EOL;
echo $dsn->getDsnValue('host') . PHP_EOL;
echo $dsn->getDsnValue('port') . PHP_EOL;
var_dump($dsn->extract()); echo PHP_EOL;