在MySQL查询中放置PHP变量

Question

I'm having issues placing a PHP variable in MySQL string,

<?php
$con=mysqli_connect("***","***","***","***");

function getItem($itemNo)
{
    if (mysqli_connect_errno())
    {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }

    $result = mysqli_query($con,"SELECT * FROM products WHERE product_id = '$itemNo'");

    echo $itemNo;
    echo "<br>";
    while($row = mysqli_fetch_array($result))
    {
        echo $row['product_id'] . " " . $row['product_name'];
        echo "<br>";
    }
}
getItem(1001);
mysqli_close($con);

?>

The page shows my echo of the $itemNo , but thats all. If I just do select * from products , it gives my entire table like it should, so I know the database is working, so I've narrowed it down to the placement of the variable.

EDIT :

product_id column is an int and also the primary key .

Answer 1

You can try a prepared statement to make using variables in your queries easier.

$stmt = $con->prepare("SELECT * FROM products WHERE product_id=?");
$stmt->bind_param($itemNo);
$stmt->execute();
$stmt->close();

Answer 2

 $result = mysqli_query($con,"SELECT * FROM products WHERE product_id = " .$itemNo );