Error Undefined offset - How to correctly display the elements of my array in my PHP Code?

Question

My method or function recurseMenu (in: UssdNode.php) normally contains the list of menus (WHICH I LOOK TO DISPLAY) contained in the variable $title=$node->getTitle():

function recurseMenu($items,$bufferLimit) {
        $objectString="<strong>". $this->getTitle() . "</strong>" . PHP_EOL;
        $lastMenu=false;
        var_dump($items);           //DEBUG "items"
        if(count($items)>0) {
            for ($i = $this->index; $i <= $bufferLimit; $i++) {
                if ($items[$i]) {
                    $item = $items[$i];
                    $num = $i + 1;
                    // get node by name
                    $userSessions = $_SESSION['userSessions'];
                    $currUserSession = $userSessions[$this->address];
                    $node = $currUserSession->getNode($item);
                    $title = $node->getTitle();
                    $objectString .= PHP_EOL . $num . '. ' . $title;
                }
            }
        } else {
            $objectString=$objectString.PHP_EOL . 'NO DATA AVAILABLE, TRY AGAIN LATER';
        }
        $lastMenu=$bufferLimit==count($items);
        $objectString=$objectString . PHP_EOL . PHP_EOL . "<strong>0. Exit</strong>";
        if($this->getParent() != '0'){
            $objectString=$objectString . PHP_EOL . "<strong>#. Back</strong>";

        }
        if($lastMenu===false){
            $rem=count($items)-$this->index;
            $objectString=$objectString . PHP_EOL . "<strong>99. Next (".$rem.")</strong>";
        }
        return $objectString;
    }

The getNode method of the UssdTree.php file:

function getNode($name){
        $node=$this->treeMenu[$name];
        return $node;
    }

And when I try the debug of $this->recurseMenu($items,$bufferLimit) in my toString method or function which displays the list of $title as strings:

function toString(){
        $objectString='';
        $items=$this->children;
        $bufferLimit=(count($items)==0)?1:$this->getBufferLimit()+1;
 
        echo "<pre>";
        print_r($this->recurseMenu($items,$bufferLimit));
        echo "</pre>";
 
        do{
            $bufferLimit-=1;
            $objectString=$this->recurseMenu($items,$bufferLimit);
        }while(strlen($objectString>160));
        $this->index=$bufferLimit;
        return $objectString;
    }

So, the problem is that nothing is displayed. And I get the following error:

Line 86 of the error I get and put below is from the UssdNode.php file which contains the statement by true of the variable if ($items[$i]) in the recurseMenu method below:

Notice: Undefined offset: 4 in C:\laragon\www\ussd\ussdmenu-server-php\UssdNode.php on line 86

When I the debug of var_dump($items); at the line 3 in my recurseMenu method or function above, I get this return:

array(4) {
[0]=>
string(5) "umeme"
[1]=>
string(4) "nwsc"
[2]=>
string(5) "paytv"
[3]=>
string(10) "paycurrent"
}

And when I edit $bufferLimit variable by removing the addition +1 at $this->getBufferLimit()+1 in the declaration of the variable $bufferLimit=(count($items)==0)?1:$this->getBufferLimit()+1; of the toString function, the menus are displayed fine but it creates another lag when pressing or issuing the request for the 99. Next key.

How to correctly display the list of menus represented by the variable $title=$node->getTitle(); in the recurseMenu method below ?

Help me fix this error.

Does this answer your question? ["Notice: Undefined variable", "Notice: Undefined index", "Warning: Undefined array key", and "Notice: Undefined offset" using PHP](https://stackoverflow.com/questions/4261133/notice-undefined-variable-notice-undefined-index-warning-undefined-arr) — Nico Haase, Sep 22 '22 at 12:43

score 0 · Accepted Answer · answered Sep 22 '22 at 12:42

The displayed error says the following:

The array $items has four items, accessible by the keys 0, 1, 2 and 3. But you are asking for key 4. This key is not there. I don't know what to do, so I am giving you an error message.

You now have two possible ways to go.

Make sure that the index ($i) is never greater than the highest index of the array.

Maybe your logic with calculating $bufferLimit is wrong, or maybe the loop is not correct. Maybe $i <= $bufferLimit needs to be $i < $bufferLimit.

Check first to see if the key you are using is actually present in the array https://www.php.net/manual/en/function.array-key-exists.php

if ($items[$i]) would need to change to if (array_key_exists($i, $items))

That way you could keep your current logic of calculating $this->index and $bufferLimit, but if the asked key is not there, the if-statement will end up being false and not throw an error.

Error Undefined offset - How to correctly display the elements of my array in my PHP Code?

1 Answers1