Getting php variable to select statement not working - php

Question

Here i am trying to pass the variable to php select query,but its not working.
couldn't figure out what is the problem.
code:
<?php
$cname = $_GET['c_name'];
include 'config.php';
$conn = mysqli_connect($dbhost, $dbuser, $dbpass, $dbname);
if(! $conn )
{
die('Could not connect: ' . mysql_error());
}
$sql = 'SELECT * FROM co_details where co_name="$cname"';
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0)
{
while($row = mysqli_fetch_assoc($result))
{
echo "<br>";
echo "Course Details <br>";
echo $row['co_name']."<br>";
echo $row['co_objectives']."<br>";
echo $row['co_outline']."<br>";
echo $row['co_prereq']."<br>";
echo $row['co_fee']."<br>";
echo $row['co_duration']."<br>";
}
mysqli_close($conn);
}
?>
what may be the reason?
Instead of variable $cname if i put the direct value then the query is executing successfully.

Answer 1

Note that single quoted strings like this one you have:
$sql = 'SELECT * FROM co_details where co_name="$cname"';
That variable that you think you have there will not get interpolated. It will only work by using double quoted strings.
$sql = "SELECT * FROM co_details where co_name='$cname'";
And as #Fred has said in the comments, stick with MySQLi including your connection error:
if(! $conn )
{
die('Could not connect: ' . mysql_error()); // mysql API doesn't belong
}
Change it to MySQLi interface:
if ($conn->connect_errno) {
die('Could not connect: ' . $conn->connect_error);
}
And you should have used prepared statements instead as this is prone to SQL injection.
<?php
if(!empty($_GET['c_name'])) {
$cname = $_GET['c_name'];
include 'config.php';
$conn = mysqli_connect($dbhost, $dbuser, $dbpass, $dbname);
if ($conn->connect_errno) {
die('Could not connect: ' . $conn->connect_error);
}
$sql = 'SELECT co_name, co_objectives, co_outline, co_prereq, co_fee, co_duration FROM co_details WHERE co_name = ?';
$select = $conn->prepare($sql);
$select->bind_param('s', $cname);
$select->execute();
$select->store_result();
$select->bind_result($co_name, $co_objectives, $co_outline, $co_prereq, $co_fee, $co_duration);
while($select->fetch()) {
echo "<br/>
Course Details: <br/>
$co_name <br/>
$co_objectives <br/>
$co_outline <br/>
$co_prereq <br/>
$co_fee <br/>
$co_duration <hr/>
";
}
}
?>

Answer 2

You can't use $cname directly in the string: try as shown below:
$sql = "SELECT * FROM co_details where co_name='".$cname."'";
Hope, it helps!

Answer 3

You are using single quote don't do like that change the query like this
$sql = "SELECT * FROM co_details where co_name='$cname'";