bindParam（），bindValue（）和execute（array（））之间的区别和优点是什么？

<?php

    $db = new PDO($dsn,$username,$password);
    $uname='avi';
    $age=19;
    $stmt = $db->prepare('INSERT INTO table(uname,age) VALUES(:uname,:age)');
    $stmt->execute(array(':uname'=>$uname,':age'=>$age));

    $stmt = $db->prepare('INSERT INTO table(uname,age) VALUES(?,?)');
    $stmt->execute(array($uname,$age));

    $stmt = $db->prepare('INSERT INTO table(uname,age) VALUES(:uname,:age)');
    $stmt->bindValue(':uname',$uname); //can be $uname or just 'avi'
    $stmt->binParam(':age',$uname); //cannot be 'avi' or value only
    $stmt->execute();

?>
<?php

    $db = new PDO($dsn,$username,$passwo