__toString does not output

Question

I found the entry PHP OOP - toString not working but it does not address my issue as I believe I am calling the magic method properly...

Here is my code:

class Alerts {

    public $message;
    public $type;
    public $output;

    public function __construct($message_id)
    {
    include 'con.php';          
    $stmt = $conn->prepare(
    'SELECT * FROM alerts WHERE id = :message_id');
    $stmt->execute(array(':message_id' => $message_id));

    while($row = $stmt->fetch(PDO::FETCH_ASSOC)){
        $this->type = $row['type'];
        $this->message = $row['message'];  
    }
    }

    public function __toString (){
        $output ='';
        $output .= "<div class='" . $this->type . "'><button class='close' data-dismiss='alert'></button>";
        $output .= "<i class='fa fa-check-circle'></i>&nbsp;<strong>";
        $output .= $this->message;
        $output .= "</strong> </div>";
        return $output;
     } 

}

It works if I call:

$message_id = 6;

$alert = new Alerts($message_id);
$output ='';
$output .= "<div class='" . $alert->type . "'><button class='close' data-dismiss='alert'></button>";
$output .= "<i class='fa fa-check-circle'></i>&nbsp;<strong>";
$output .= $alert->message;


$output .= "</strong> </div>";

on the page but not if I use:

$message_id = 6;

$alert = new Alerts($message_id);
echo $alert->output;

I am a newbie with PHP OOP so you help is greatly appreciated

The __toString() method is automatically called when an object is used in the context of a string. Just do echo $alert; — sjagr
– sjagr, Commented Jan 21, 2015 at 16:12
Not sure why you think you need ->output... No language I know uses that to invoke toString. — Niet the Dark Absol
– Niet the Dark Absol, Commented Jan 21, 2015 at 16:12
Also don't forget if you're trying to actually modify the public property $output, you must use $this->output in the context of a method. — sjagr
– sjagr, Commented Jan 21, 2015 at 16:17

sjagr · Accepted Answer · 2015-01-21 16:19:40Z

1

From the PHP docs:

The __toString() method allows a class to decide how it will react when it is treated like a string. For example, what echo $obj; will print. This method must return a string, as otherwise a fatal E_RECOVERABLE_ERROR level error is emitted.

By that logic, doing echo $alert->output; will just output the blank property public $output; that was declared in your class. Two reasons that public $output is blank and doesn't get modified is:

You don't access $this->output in the context of the __toString() method.
__toString() doesn't get called when you access any method or property of the object, only when you treat an object like a string.

What you actually should do if you decide to utilize __toString() is:

echo $alert;

answered Jan 21, 2015 at 16:19

sjagr

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9 Comments

Twiggit Over a year ago

Hi sjagr, Thanks you for your reply I did as you suggested and used echo $alert and it printed out but the I get the error after: Catchable fatal error: Method Alerts::__toString() must return a string value in /var/www/vhosts/dev-roe-vti.org/httpdocs/mdashboard/login.php on line 130

sjagr Over a year ago

@janetspagnol You're welcome. If my solution helped you, it is appropriate to mark off the solution as accepted by clicking the grey checkmark below the up/down arrows to the left of my answer so that it turns green. See this meta article for more info

Twiggit Over a year ago

Here is the var_dump if it helps object(Alerts)#3 (2) { ["message"]=> string(78) "We are sorry but we do not have a Senior Mentor that matches these credentials" ["type"]=> string(18) "alert alert-danger" }

sjagr Over a year ago

@janetspagnol Did you modify your __toString() method? As the error says, you must be returning something other than a string. Either way, this should be addressed in a new question as it is unrelated to this question.

sjagr Over a year ago

@janetspagnol The var_dump is not helpful at all. What is in your __toString() method?

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