gistfile1.php

<?php
    $conn = new PDO("mysql:host=127.0.0.1;dbname=rfid;", "root", "");
    $cursor = $conn->prepare("select * from :table ;");
    //$cursor->execute(array(":table"=>"contrast"));
    $cursor->bindValue(":table", "contrast");
    $cursor->execute();

    var_dump($cursor->fetch());
    // var_dump($cursor);

    // var_dump($conn->query("select * from contrast")->fetch());

?>