PHP object/variable error

Question

Disclaimer: I'm new to object-oriented PHP and I'm generally terrible at the language.

So I've got a class called "Page" in a file (class_lib.php) and I've created this variable and written a while/for loop that processes it when its set:

public $extra= "";
if (isset($this->extra)) {
echo "<table id=\"tab\">";
while (list($counter) = each($this->$extra)) {
    for ($i=0;$i<3;$i++) {
    echo "<tr class=\"tl\">";
    echo "<td>$counter[$i]</td>";
    echo "</tr>";
    }
}
}

On one page, I need a table printed out. The data for this is in an array:

$page->extra = array( array('Track no.', 'Track title', 'Track length'),
                      array('01', 'Value1', 'No1'),
                      array('02', 'Value2', 'No2'),
                      array('03', 'Value3', 'No3'),
                      array('04', 'Value4', 'No4'),
                      array('05', 'Value5', 'No5'),
                      array('06', 'Value6', 'No6'),
                      array('07', 'Value7', 'No7'),
                      array('08', 'Value8', 'No8'),
                      array('09', 'Value9', 'No9'),
                      array('10', 'Value10', 'No10'),
                      array('11', 'Value11', 'No11'),
                      array('12', 'Value12', 'No12')
                     );

The errors I'm getting are:

Notice: Undefined variable: extra in C:\wamp\www\test\class_lib.php on line 47

...and:

Fatal error: Cannot access empty property in C:\wamp\www\test\class_lib.php on line 47

Here's the full class_lib.php file if needed: http://pastebin.com/7XRjDKVU

...and the index.php: http://pastebin.com/yHBYpNxd

I hope I've given enough information there - I'd appreciate any help.

Kęstutis · Accepted Answer · 2011-09-06 20:42:50Z

2

you misstyped variable:

while (list($counter) = each($this->$extra)) {

should be

while (list($counter) = each($this->extra)) {

look at $this->extra

answered Sep 6, 2011 at 20:42

Kęstutis

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4 Comments

Dan Over a year ago

Okay thanks, that removed the error, now I get a table with a very small width of about 2px without any values in it. Must be something wrong with the loop...

Dan Over a year ago

One thing though: now on every other page where I don't have a table and I haven't re-set $extra, the error: Warning: Invalid argument supplied for foreach() in C:\wamp\www\test\class_lib.php on line 47 is displayed. Is there anyway to get around this? Can I add an else and get it to continue on without inserting anything for $extra?

Kęstutis Over a year ago

change if (isset($this->extra)) to if (count($this->extra))

Dan Over a year ago

Oh, it's good - I just removed the $extra variable from the class_lib.php so that it was only set on the pages I needed it to be set on. I though you had to create the variable and then overwrite it you see. Thanks for the help :)

George Cummins · Accepted Answer · 2011-09-06 20:41:51Z

1

$this->$extra

should be:

$this->extra

answered Sep 6, 2011 at 20:41

George Cummins

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2 Comments

Dan Over a year ago

Okay thanks, that removed the error, now I get a table with a very small width of about 2px without any values in it. Must be something wrong with the loop...

George Cummins Over a year ago

According to your posted code, you are attempting to access $this->extra before it has been populated with data. You will need to insert your arra of data first, then access it.

Farray · Accepted Answer · 2011-09-06 21:15:09Z

In addition to what others have written about $this->extra, you're mis-using list() and $counter.

According to the PHP docs, list() is used to assign multiple variables from 1 array object.

The problem is with this line:

list($counter) = each($this->extra)

What happens is that each() pulls the next key->value pair from your $this->extra data. Then list() populates $counter with the first value from the pair, which is the Key value. Since $counter is now holding the int value of the Key, it can't be used as an array (and silently fails, echoing an empty character).

Try rearranging it like this:

echo '<table id="tab">';
foreach( $this->extra as $value) // ignores the Key and just gets the Value as $row
{
    list( $number, $name, $length ) = $value;  //populates $number, $name, $length from $row
    echo '<tr class="tl">';
    echo '<td>' . $number . '</td>';
    echo '<td>' . $name. '</td>';
    echo '<td>' . $length . '</td>';
    echo '</tr>';
}
echo '</table>';

You could also use foreach( $this->extra as $key=>value ) if you need the Key value.

galchen · Accepted Answer · 2011-09-06 20:57:08Z

0

$counter gets the index. you must put

while (list($i,$counter) = each($this->extra))

or

foreach($this->extra as $counter) {

this is because each returns key value pair:

Returns the current key and value pair from the array array.

answered Sep 6, 2011 at 20:57

galchen

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