PHP/MySQL where clause returning an empty value

Question

I have a small problem using the Where clause for PHP/MySQL in the code shown below:

<?php
$con=mysqli_connect("host","username","password","database");
//Note that I have replaced my parametres just for this question
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
//Request Session ID
$id = $_SESSION['uid'];
echo "Session ID = ' . $id;
echo "<br>";
//Request Username
echo "Username = " . mysqli_query($con,"SELECT username FROM 'users' WHERE id = 4");

?>

The output of this is (after logging in on my separate login page):

Session ID = 4

Username =

So it is evident that there is an issue with the where clause. There is no issue with the connection parametres as far as I am aware. When I run the MySQL command in PHPmyadmin I get the expected result of 'Admin'. My inputs are correctly named.

I have no idea what is causing this and I can't find any similar problems on the forum. Any help would be appreciated. Thanks.

UPDATE

I have adapted the below answers to make this code:

<?php
// Only run this script if the sendRequest is from my flash application
if ($_POST['sendRequest'] == "parse") {
//conection:
$con=mysqli_connect("mysqlXX.000webhost.com","a4935911_***","***","a4935911_***");
$id = $_SESSION['uid'];
$getuname = mysqli_fetch_assoc(mysqli_query($con, "SELECT username FROM users WHERE id = $id"));
$uname = $getuname ['username'];

// Print 1 var to flash
print "var1=The username of this user is $uname.";

}

?>

Which is triggered by my flash application. This works fine if I do not use session ID variable and just use e.g. 4 as my id value but I need to use the session ID for this. Any ideas what is up with this?

Marcel Korpel · Accepted Answer · 2013-10-25 13:27:29Z

2

You shouldn't surround table names with ordinary single quotes ('); use backticks instead (or, if you don't use reserved words, none). So:

SELECT username FROM `users` WHERE id = 4

or

SELECT username FROM users WHERE id = 4

Moreover, mysqli_query doesn't return the result in the field, but a mysqli_result object. You'll have to use a fetch command to get the result(s), e.g.

$result = mysqli_query($con,"SELECT username FROM 'users' WHERE id = 4");
$row = mysqli_fetch_assoc($result);
echo 'Username = ' . $row['username'];

edited Oct 25, 2013 at 13:27

answered Oct 25, 2013 at 13:21

Marcel Korpel

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3 Comments

user2867893 Over a year ago

That has done something. I believe I'm getting an output now but there is an issue as follows: Catchable fatal error: Object of class mysqli_result could not be converted to string in /home/a4935911/public_html/usersOnline.php on line 116

Marcel Korpel Over a year ago

@user2867893 I wasn't finished answering, look at the updated answer.

user2867893 Over a year ago

Alright, I see. That's what I tried when I originally made this script but I got issues with that so I changed to this. I'm not very good at PHP so I don't know what is intended by these: Warning: mysqli_query() expects parameter 1 to be mysqli, resource given in /home/a4935911/public_html/usersOnline.php on line 115 Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, null given in /home/a4935911/public_html/usersOnline.php on line 116

Sam Geeks · Accepted Answer · 2013-10-25 13:34:06Z

0

You should use the following code:-

//conection:
$con=mysqli_connect("host","username","password","database");

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

$getuname = mysqli_fetch_assoc(mysqli_query($con, "SELECT username FROM users WHERE id = 4"));
$username = $getuname ['username'];

 //Request Username
 echo "Username = " .$username ;

answered Oct 25, 2013 at 13:34

Sam Geeks

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3 Comments

user2867893 Over a year ago

YEAH! That's it. I wasn't aware that mysqli_query doesn't actually return the value I need as you and @MarcelKorpel point out. Thank you both for your answers.

user2867893 Over a year ago

I could actually use with a bit of further help on this as shown in my update please.

Sam Geeks Over a year ago

What you get when you echo session uid?

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