Fatal error.. Call to a member function.. on a non-object

Question

I have a GCM class which includes a send_notification function. In a different class, Demand.php, I am trying to use the send_notification function. So I have a constructor in Demand.php which points to my GCM class like this:

 $gcm = new GCM();

This $gcm variable is used in a function inside that class like this:

$result = $gcm->send_notification($registatoin_ids, $message);

That's where I get the error:

<br />n<b>Fatal error</b>:  Call to a member function send_notification() on a non-object in..

I searched for the problem and found out that the problem is that $gcm is null and that's why it's calling nothing. So when I put the

$gcm = new GCM();

Inside my function it worked correctly. But is there no other way of doing this? I mean should it not be alright only by putting creating $gcm in the constructor of Demand.php?

Here are the parts where I am referring to:

function __construct() {
    require_once 'GCM.php';
    require_once 'DB_Connect.php';
    require_once 'DB_Functions.php';
    // connecting to database
    $this->db = new DB_Connect();
    $this->db->connect();
    $gcm = new GCM();
    $df = new DB_Functions();

}

// destructor
function __destruct() {

}


public function getDistance($uuid, $name, $distance, $latstart, $lonstart, $latend, $lonend, $gcm_regId) {
    $user_new = array ("$uuid", "$name", "$distance","$latstart", "$lonstart", "$latend", "$lonend","$gcm_regId");  
    $query = sprintf("SELECT uid, distance,latstart, lonstart, latend, lonend, gcm_regid, name FROM user_demand WHERE latstart='%s' AND lonstart='%s'",
    mysql_real_escape_string($latstart),
    mysql_real_escape_string($lonstart));
    $user = mysql_query($query);

    $no_of_rows = mysql_num_rows($user);

    while($user_old = mysql_fetch_assoc($user))
    {
        $djson = $this->findDistance($latend,$lonend,$user_old["latend"],$user_old["lonend"] );

        if ($user_old["distance"]+$distance>=$djson) {
            $match = mysql_query("INSERT INTO matched_users(gcm_a, gcm_b, name_a, name_b) VALUES(".$user_old['gcm_regid'].",".$user_new['gcm_regId'].",".$user_old['name'].",".$user_new['name'].")");
            $registatoin_ids = array($gcm_regId);
            $message = array("var" => $name);
            $result = $gcm->send_notification($registatoin_ids, $message);
        }
    }
}

This sounds like a misunderstanding about scoping. Can you show us where you've put $gcm = new GCM(); relative to $gcm->send_n..? — Halcyon
– Halcyon, Commented Jan 9, 2013 at 17:01
Do not discount debugging tools like Xdebug and var_dump , try those to see what values you have at that instant — pal4life
– pal4life, Commented Jan 9, 2013 at 17:03
$gcm = new GCM(); will only exist in the current scope. You can set it to an instance variable so it can be accessed throughout the class: $this->gcm = new GCM() — MrCode
– MrCode, Commented Jan 9, 2013 at 17:04

Stu · Accepted Answer · 2013-01-09 17:03:59Z

9

If you put $gcm = new GCM(); in the constructor of your Demand class, then the variable $gcm will only be available in the constructor method.

If you want to be able to access the $gcm variable throughout the Demand class you'll need to set it as a property of the class like so:

class Demand()
{
    /**
     * Declare the variable as a property of the class here
     */
    public $gcm;

    ...
    function __construct()
    {
        ...
        $this->gcm = new GCM();
        ...
    }

    function myFunction()
    {
        ...
        // You can access the GCM class now in any other method in Demand class like so:
        $result = $this->gcm->send_notification($registatoin_ids, $message);
        ...
    }
    ...
}

answered Jan 9, 2013 at 17:03

Stu

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1 Comment

user1732457 Over a year ago

Thank you very much, it worked great, i am new in php, and i am missing basic knowledge, very helpful

aziz punjani · Accepted Answer · 2013-01-09 17:03:05Z

3

gcm will only be available in the scope of the constructor unless you initialize it as a instance variable.

class Demand
{
    private $_gcm; 
    function __construct() 
    {
        $this->_gcm = new GCM(); 
    }

    function youWantToUseGcmIn()
    {
        $this->_gcm->send_notification(.....); // access it like this 
    }
}

answered Jan 9, 2013 at 17:03

aziz punjani

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1 Comment

user1732457 Over a year ago

Thank you very much, it worked, i am just new in php, and missing some basic knowledge..

Marc B · Accepted Answer · 2013-01-09 17:05:40Z

0

You create $gcm in an object constructor, then use it from some other method in the same class? You're not storing it properly, then. You have to do:

class X {
    function constructor() {
        $this->gcm = new GCM();
    }

    function other_method() {
        $this->gcm->send_notification(...);
    }
}

if you have

function constructor() {
    $gcm = new GCM();  <-- this is just a temporary local variable.
}

all you're doing is creating a local variable within the constructor, which will be destroyed as soon as the constructor returns. Saving the new object in $this->gcm saves it inside the containing object and makes it available to other methods.

answered Jan 9, 2013 at 17:05

Marc B

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Comments

Techie · Accepted Answer · 2013-01-09 17:06:20Z

0

This means $gcm is not an object, probably it's NULL or false in some cases (nothing found) due to it's not accessible. Out of scope

answered Jan 9, 2013 at 17:06

Techie

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