Question

I run a php script on a page which looks for certain classes/elements and I may sometimes get a “Trying to get property of non-object” error if the class/element does not exist.

I want to know how I can handle this error so that I can assign my own null value to a variable as using if statements or is_null does not seem to do the trick.

check out my code below for a better understanding of what I mean.

on the line if($size = $elem->find('.size',0)->plaintext) and error will be thrown for the ‘history’ element because the class size does not exist.

function:getInfo

function getInfo($link){
   $page = file_get_html($link);        

   if($page){       
      $categoryLink = array();
      $categoryName = array();
      $categorySize = array();

      if($container = $page->find('.infoContainer',1)){

         foreach($container->find('.element') as $elem){

            if($link = $elem->find('a',0)->href){   
               $categoryLink[] = $link;
            }else{
               $categoryLink[] = "";
            }

            if($name = $elem->find('.name',0)->plaintext){
               $categoryName[] = $name;
            }else{
               $categoryName[] = "";
            }

            if($size = $elem->find('.size',0)->plaintext){
               $categorySize[] = $size;
            }else{
               $categorySize[] = 0;
            }
         }
      }
   }
}

http://www.example.com

<div class='infoContainer'>
   <div class='element'>
      <a href='www.example.com/physics'>
      <div class='name'>physics</div>
      <div class='size'>1000</div>
   </div>
   <div class='element'>
      <a href='www.example.com/math'>
      <div class='name'>math</div>
      <div class='size'>800</div>
   </div>
   <div class='element'>
      <a href='www.example.com/history'>
      <div class='name'>history</div>
   </div>

</div>

call function

getInfo("www.example.com");

Answer 1

You should first check the result of find before attempting to access its properties:

$result = $elem->find('foo', 0);
if ($result) {
    $something = $result->property;
}

This applies to all 3 checks inside the foreach, only with different parameter names etc.