Classes/OO in php

[AllofHumanity]

I recently found a little guide/tutorial about OOP in php. I followed it and I was able to re-create the guide to something I can use but I'm running into a problem. I try to use the database connection from the __construnt function but it doesn't want to work. I get a Fatal error: Call to a member function execute() on a non-object in D:\allofhum\xampp\htdocs\allofhum\classes\Mysql.php on line 65. I'm not quite sure why, I would love some help.

<?phprequire_once '../includes/constants.php';class Mysql {    private $conn;    function __construct(){        $this->conn = new mysqli(DB_SERVER, DB_USER, DB_PASSWORD, DB_NAME)                    or die('There was a problem connecting to the DB');    }    //End   __construct    function verify_Username_and_Pass($un, $pwd){        $query = "SELECT *            FROM users            WHERE username = ?            AND password = ?            LIMIT 1";        if($stmt = $this->conn->prepare($query)){            $stmt->bind_param('ss', $un ,$pwd);            $stmt->execute();            if($stmt->fetch()){                $stmt->close();                return true;            }        }    }    //End verify_Username_and_Pass    function checkContent($file){        print "checking";        $maxsize = 2097152;        $size = $maxsize / 1024;        if ((($file["type"] == "image/gif")        || ($file["type"] == "image/jpeg")        || ($file["type"] == "image/png"))        && ($file["size"] < $maxsize)){        return true;        }             else print "Invalid filetype and or size.<br />Size:". $file["size"] / 1024 . "kb  Max size:". $size." kb";    }    //End checkContent        function addContent($switch, $file, $heading, $desc){        print $switch;        $target = "../images/content/";        $target = $target . basename($file['name']);        if(file_exists($target . $file['name'])){            print $file['name'] . " already exists.";        } else{           $success_up = move_uploaded_file($file["tmp_name"], $target);           if($success_up){            print "<br /> File Uploaded";            $time = time();            $query = "INSERT INTO $switch             (  `pic` ,                `heading` ,                `desc` ,                `time`)            VALUES            ( `$file[name]`, `$heading`, `$desc`, `$time` )";                  $stmt = $this->conn->prepare($query);           $stmt->execute(); //ERROR IS HERE            $stmt->close();               return true;                        }                }            }    //End addContent    }    //End class Mysql?>

[justsomeguy]

The reason that the error is here:

$stmt = $this->conn->prepare($query);$stmt->execute(); //ERROR IS HERE

is because the SQL query failed, so the prepare method returned false. Since $stmt got set to the return of prepare, and the return value was false, $stmt got set to false so that's why the error said it's not an object. That means there's an error in the SQL query. You can get the error message like this:$stmt = $this->conn->prepare($query) or exit($this->conn->error());In this case, the problem is that you have the values surrounded with `backticks`, they should be regular 'single quotes'; only table names, database names, etc use backticks.

[AllofHumanity]

In this case, the problem is that you have the values surrounded with `backticks`, they should be regular 'single quotes'; only table names, database names, etc use backticks.

Oh I see. I'm glad was something simple. Thank you, you just made me a very happy guy.