How to avoid 'undefined index' errors? [duplicate]

Answer 1

Set each index in the array at the beginning (or before the $output array is used) would probably be the easiest solution for your case.

Example

$output['admin_link'] = ""
$output['alternate_title'] = ""
$output['access_info'] = ""
$output['description'] = ""
$output['url'] = ""

---

Also not really relevant for your case but where you said you were new to PHP and this is not really immediately obvious isset() can take multiple arguments. So in stead of this:

if(isset($var1) && isset($var2) && isset($var3) ...){
    // all are set
}

You can do:

if(isset($var1, $var2, $var3)){
   // all are set 
}

Answer 2

foreach($i=0; $i<10; $i++){
    $v = @(array)$v;   
    // this could help defining $v as an array. 
    //@ is to supress undefined variable $v

    array_push($v, $i);
}

Answer 3

A short solution is this (PHP 5.3+):

$output['alternate_title'] = $output['alternate_title'] ?:'';

You get either the value of the variable, if it doesn't evaluate to false, or the false expression. (The one after the ':')

Using the ternary Operator, without the "if true" parameter, will return the result of the test expression (The first one ) Since undefined evaluates to false, the false expression will be returned.

In PHP 7 there is the slightly more elegant Null coalescing operator:

$output['alternate_title'] = $output['alternate_title'] ?? '';

(It would be nice with a default assignment operator like '?=')

Answer 4

You could try using a nice little function that will return the value if it exists or an empty string if not. This is what I use:

function arrayValueForKey($arrayName, $key) {
   if (isset($GLOBALS[$arrayName]) && isset($GLOBALS[$arrayName][$key])) {
      return $GLOBALS[$variable][$key];
   } else {
      return '';
   }
}

Then you can use it like this:

echo ' Values: ' . arrayValueForKey('output', 'admin_link') 
                 . arrayValueForKey('output', 'update_frequency');

And it won't throw up any errors!

Hope this helps!