Description:
------------
When the passowrd is string("") and set ATTR_PERSISTENT is true, the PDO __construct where Fatal Error (You keep press the F5 in the browser , U will see the error some times)
If password is not empty or is null , it's ok.

$dsn = 'mysql:dbname=test;host=localhost;port=3306';
$user = 'root'; 
$password = "";//will wrong
//$password = null; //will ok     
                
try {
    $dbh = new PDO($dsn, $user, $password,
        array( 
            \PDO::ATTR_PERSISTENT => true
        )   
    );  
} catch (PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}   

Test script:
---------------
<?php           
/* Connect to an ODBC database using driver invocation */
$dsn = 'mysql:dbname=test;host=localhost;port=3306';
$user = 'root'; 
$password = "";
                
$dbh = new PDO($dsn, $user, $password,
    array(
        \PDO::ATTR_PERSISTENT => true
    )   
);  
print_r($dbh);