Edit report at https://bugs.php.net/bug.php?id=55772&edit=1

 ID:                 55772
 Comment by:         anonymous at nowhere dot never
 Reported by:        rick dot foos at solengtech dot com
 Summary:            is_array throws E_NOTICE on undefined array
                     elements, isset does not.
 Status:             Open
 Type:               Bug
 Package:            Scripting Engine problem
 Operating System:   Fedora/Ubuntu
 PHP Version:        5.3.8
 Block user comment: N
 Private report:     N

 New Comment:

>is_array is the correct call to use.

What are you blithering about? I think you mean isset(). is_array has nothing 
to do with it.

Anyway, the problem you're having is because you're treating $data_array as a 
multidimensional array. It's not. PHP has arrays of arrays, not 
multidimensional arrays (in languages like this you could make a triangular 
array if you wanted). So if the row is not defined then testing isset on the 
row's column will complain about the undefined row. So you have to isset on the 
row to make sure that's there first before you can test its column elements.

E.g.:

if (isset($data_array[$r + 1]) && isset($data_array[$r + 1][$c + 1])) ...

Or like this:

for ($r = 0; $r < $row_count; $r++) {
        echo "<tr>";
        if (isset($data_array[$r + 1])) {
                $row = $data_array[$r + 1];
                for ($c = 0; $c < $col_count; $c++) {
                        if (isset($row[$c + 1])) {
                                $data = $row[$c + 1];
                        } else {
                                $data = null;
                        }
                        echo "<td>", $data;
                }
        } else {
                echo str_repeat("<td>", $col_count);
        }
}


Previous Comments:
------------------------------------------------------------------------
[2011-09-24 00:29:27] rick dot foos at solengtech dot com

Description:
------------
I have a sparse matrix, that needs each element to display on an html page. So 
when the matrix is loaded with defined values there are many undefined values, 
6158 for example.

This is displayed as a square matrix using an HTML table - A conflict between 
good PHP programming and HTML programming. The undefined elements need some 
html, so the 'for loops' must touch each element of the array to display the 
square set of values.

is_array is the correct call to use. It tests array elements, and returns true 
or false if they are valid or not.

While the is_array function returns true and false - PHP still issues the 
warning message. is_array is a test, not an operation on a null value, and 
therefore not bad programming requiring a message.

http://rickfoosusa.blogspot.com/2011/09/howto-clear-php-undefined-offset.html

Test script:
---------------
$data_array=array();
$data_array[2][10] = "defined";
$row_count = 10;
$col_count = 10;

//...fill with the defined values...many values undefined.

for ($r = 0; $r < $row_count; $r++)
{
echo "<tr>";
  for ($c = 0; $c < $col_count; $c++)
  {
     if (isset($data_array[$r+1][$c+1])){
       $data = $data_array[$r+1][$c+1];
     } else {
       $data = NULL;
     }
    echo "<td>";
  }
} 

Expected result:
----------------
True or False depending if the array element is valid.

Actual result:
--------------
True or False depending if the array element is valid.

PHP Notice:  Undefined offset: 118 in /usr/share/resultsdb/www/index.php on 
line 465, referer: http://134.86.96.216/resultsdb/index.php?



------------------------------------------------------------------------



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