How to remove double quotes in a shortcode?

do a print_r to your $a variable, there you see everything that is happening

echo '<pre>';
print_r($a);
echo '</pre>';
die();

this way you can see if the url variable has double quotes, because it seems it doesnt have.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)