“Can't use function return value in write context” error in PHP

StackOverflow https://stackoverflow.com/questions/3888376

Question

Fatal error: Can't use function return value in write context in line 3,

In which cases such errors get triggered?

My program: 

 //QUERY VARIABLE
 $query="select * form user where user_name='$user_name' and user_password='sha($user_password)'";

 //ESTABLISHING CONNECTION
 $result=mysqli_query($dbc,$query)or die('Error Querying Database');

 while($row=mysqli_num_rows($result)==1)
 {
  //SET COOKIE
  setcookie('user_name',$row['user_name']);
  setcookie('user_id',$row['id']);
  $query="select * form user";
  $result=mysqli_query($dbc,$query)or die('Error Querying Database');
  $page_url='http://'.$_SERVER['HTTP_HOST'].dirname($_SERVER['PHP_SELF']).'/index.php';
  header('Location'.$page_url);
 }

 //TERMINATING CONNECTION
 mysqli_close($dbc);
 }
 else
 {
  $error_msg='Please type both user name and password correctly to login';
 }
//}
}
else
{
 $page_url='http://'.$_SERVER['HTTP_HOST'].dirname($_SERVER['PHP_SELF']).'/register.php';
 header('Location'.$page_url);
}
}
if($output_form)
{
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
 <title>Mismatch - Log In</title>
 <link rel="stylesheet" href="stylesheets/style.css" media="all" />
</head>
<body class="body_style">
 <?php
 echo('<label class="signin_label">'.$error_msg.'</label>');
 ?>

<h2>Mismatch - Where Matches Happen...</h2>
<fieldset>
 <legend>Mismatch - Log In</legend>
 <form method="post" action="<?php $_SERVER['PHP_SELF']; ?>"><!--Self Referencing Form-->
 <label class="signin_label">USER NAME</label>
 <input type="text" name="user_name" title="Enter Your Account User Name" class="signin_textbox" value="<?php if(!empty($_POST['user_name']))$_POST['user_name']; ?>" /><br />
 <label class="signin_label">PASSWORD</label>
 <input type="password" name="user_pwd" title="Enter Your Account Password" class="signin_textbox" value="" /><br />
</fieldset>
 <input type="submit" name="login_submit" title="Click To Log In" value="Log In" class="button" />
<?php
}
?>
</body>
</html>
Was it helpful?

Solution

Try changing

if(!isset($_COOKIE(user_id)))

to

if(!isset($_COOKIE['user_id']))
                  ^^       ^^

$_COOKIE is an associative array.

OTHER TIPS

I've tidied up your code here:

<?php

//CLEAR THE ERROR MESSAGE
$error_msg = '';

//CHECK TO SEE IF COOKIE IS SET
if ( ! isset($_COOKIE['user_id']))
{
    $output_form = TRUE;

    if (isset($_POST['login_submit']))
    {
        //GRAB DATA
         $user_name = $_POST['user_name'];
         $user_password = $_POST['user_pwd'];

        if ( ! empty($user_name) && ! empty($user_password))
        { 
            //DATABASE CONNECTION VARIABLE
            $dbc = mysqli_connect('localhost','root','','mismatch') or die('Error Connecting To Database');

            //QUERY VARIABLE
            $query = 'SELECT id FROM `user` WHERE user_name = \''.mysql_real_escape_string($user_name).'\' and user_password = \''.sha($user_password).'\'';

            //ESTABLISHING CONNECTION
            $result = mysqli_query($dbc,$query) or die('Error Querying Database');

            if (mysql_num_rows($result)) {
                $row = mysql_fetch_assoc($result);

                //SET COOKIE
                setcookie('user_name', $user_name);
                setcookie('user_id', $row['id']);
                header('Location: /index.php');
                die();
            }
                    else {
                        $error_msg = 'Please type both user name and password correctly to login';
                    }

            //TERMINATING CONNECTION
            mysqli_close($dbc);
        }
        else {
            $error_msg = 'Please type both user name and password correctly to login';
        }
    }
    else {
        header('Location: /register.php');
        die();
    }
}

if ($output_form)
{

?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
    <head>
        <title>Mismatch - Log In</title>
        <link rel="stylesheet" href="stylesheets/style.css" media="all" />
    </head>
    <body class="body_style">
        <?php
            echo '<label class="signin_label">'.$error_msg.'</label>';
        ?>
        <h2>Mismatch - Where Matches Happen...</h2>
        <fieldset>
        <legend>Mismatch - Log In</legend>
        <form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>"><!--Self Referencing Form-->
        <label class="signin_label">USER NAME</label>
        <input type="text" name="user_name" title="Enter Your Account User Name" class="signin_textbox" value="<?php if(!empty($_POST['user_name'])) echo $_POST['user_name']; ?>" /><br />
        <label class="signin_label">PASSWORD</label>
        <input type="password" name="user_pwd" title="Enter Your Account Password" class="signin_textbox" value="" /><br />
        </fieldset>
        <input type="submit" name="login_submit" title="Click To Log In" value="Log In" class="button" />
    </body>
</html>
<?php

}

?>

Some problems I can remember finding:

  • $_COOKIE(user_id) instead of $_COOKIE['user_id']
  • No escaping on MySQL input
  • Big problem with your while() clause. I've replaced this with an if and mysql_fetch_assoc()
  • SQL queries said form not FROM

There were some others too that I've probably forgotten about.

Enjoy!

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