Error Binding Parameter On PHP/MySQLi

Question

I am trying to create an insert statement using data posted from the previous page and binding them to the statement

My SQL insert statement is this:

// insert new user
$db = createConnection();
$insertquery="insert into comments (com, userid, comdate, blogpost) values (?,?,?,?)";
$inst=$db->prepare($insertquery);
$inst->bind_param("sisi", $comment, $user, $today, $id);
$inst->execute();
$inst->close();

When I turn on debugging for PHP this is the error I receive

Fatal error: Call to a member function bind_param() on boolean in /blog/xcomment.php on line 29

The data that is being passed in for the bind_param is

Array ( [comment] => My New Comment [blogid] => 1 ) 2016-01-07 12:31:50

$user = $currentuser['userlevel'];
$comment = $_POST['comment'];
$id = $_POST['blogid'];
$today = date("Y-m-d H:i:s");

Answer 1

尝试改用单引号：

$inst->bind_param('sisi', $comment, $user, $today, $id);

Answer 2

http://php.net/manual/en/mysqli-stmt.prepare.php

$db->prepare - return boolean.

it's correct usage:

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$city = "Amersfoort";

/* create a prepared statement */
$stmt =  $mysqli->stmt_init();
if ($stmt->prepare("SELECT District FROM City WHERE Name=?")) {

    /* bind parameters for markers */
    $stmt->bind_param("s", $city);

    /* execute query */
    $stmt->execute();

    /* bind result variables */
    $stmt->bind_result($district);

    /* fetch value */
    $stmt->fetch();

    printf("%s is in district %s\n", $city, $district);

    /* close statement */
    $stmt->close();
}

/* close connection */
$mysqli->close();
?>