使用PHP更改XML文件的值 - 某个子项

Question

everybody! My problem is as follows: I am using an xml file with products info. Here it is - example.xml

    <?xml version="1.0" encoding="ISO-8859-1"?>
<products>
    <item>
        <name>Flat Screen Television SONY KDL-4500WEED</name>
        <image>http://img.zap.co.il/pics/2/7/9/2/37682972c.gif</image>
        <description>This is our newest TV set from the SONY Comp. and we hope you buy it mothefuckerzzzz....zasdhaskjdhkahdca a dsah dha adlasldoao al ladjjada</description>
        <left>17</left>
    </item>
    <item>
        <name>Aiwa ozvuchitelna sistema</name>
        <image>http://crev.vo.llnwd.net/o42/audioreview/images/products/product_119021.jpg</image>
        <description>This is our newest TV set from the Aiwa Comp. and we hope you buy it mothefuckerzzzz....zasdhaskjdhkahdca a dsah dha adlasldoao al ladjjada</description>
        <left>12</left>
    </item>
    <item>
        <name>Blu-Ray DVD Player Panasonic</name>
        <image>http://news.cnet.com/i/bto/20070725/BD-UP5000_overhead.jpg</image>
        <description>This is our newest TV set from the Aiwa Comp. and we hope you buy it mothefuckerzzzz....zasdhaskjdhkahdca a dsah dha adlasldoao al ladjjada</description>
        <left>33</left>
    </item>
    <item>
        <name>DURO na SHISH...</name>
        <image>http://media.otkrovenia.com/profiles/DureFF.jpg</image>
        <description>This is our newest TV set from the Aiwa Comp. and we hope you buy it mothefuckerzzzz....zasdhaskjdhkahdca a dsah dha adlasldoao al ladjjada</description>
        <left>18</left>
    </item>
</products>

The idea is that a User can reserve numbers of the products by a php page, which will automatically tell him how many are left and change the values of the xml file of the certain products. Here is my php page - metro.php:

    <?php
    $products = simplexml_load_file("example.xml");
    $max_per_row = 2;
    $item_count = 0;

echo '<table width="100%" border="0" cellspacing="2" cellpadding="2"><tr>';
    foreach ($products->item as $item)
{
    if ($item_count == $max_per_row)
    {
        echo "</tr><tr>";
        $item_count = 0;
    }
    echo '<form name="reg" action="metro2.php" method="post"><td width="50%"><b>Name:</b>&nbsp;<input name="fname" maxlength="256" value=" ', $item->name , '" readonly style="width: 300px; border:0;" /><br><img src="' , $item->image, '" alt="Product" height="200"><br>' , '<b>Description:</b>&nbsp;',  $item->description , '<br><b>Left:</b>&nbsp;<input name="left" maxlength="7" value="' , $item->left ,'" readonly style="width: 70px; border:0;" /><br>
  <label>
  <input type="submit" name="button" id="button" value="Reserve!" />
  </label>
</form><br><hr /></td>', PHP_EOL;

    $item_count++;
}
   echo '</tr>
</table>';
?>

And here is the PHP page for the action of the form. This is metro2.php:

 <?php  
$products = simplexml_load_file("example.xml");
$fname = $_POST['fname'];
$left = $_POST['left'];
$new_left = $left - 1;
echo 'You want to reserve&nbsp;<b>', $fname, '</b>.<br />';
echo 'There are now only&nbsp;<b>', $new_left, '</b>&nbsp;of this product.';
$products->item->left = $new_left;
$products->asXML("example.xml");
?>

The problem is as follows. If we assume that I have 33 Aiwas and 17 SONYs, if I hit Reserve! for an Aiwa it gives me on metro2.php that 32 Aiwas, remain, but CHANGES THE VALUE of the LEFT ITEMS for the SONY, so when I reload the page metro.php it gives me that I have 33 Aiwas and 32 SONYs... It clearly does not change the value of the correct child of the products... Where is my mistake. I guest somewhere in page metro2.php... But i donno what to do... Please help :) Thanks in advance!

Answer 1

You must select the correct child in metro2.php. The best solution is you add the index opf current child as a hidden input field in metro.php. In metro2.php you can take the the index and select the correct child to set the new value.

EDIT:

I take the code above and add the changes:

metro.php:

<?php
$products = simplexml_load_file("example.xml");
$max_per_row = 2;
$item_count = 0;

echo '<table width="100%" border="0" cellspacing="2" cellpadding="2"><tr>';

// Change the type of loop for access the items manually and get the correct index.
for ($index = 0, $count = $products->count(); $index < $count; $index++)
{
    // Get the item by index
    $item = $products->children()[$index];
    if ($item_count == $max_per_row)
    {
        echo "</tr><tr>";
        $item_count = 0;
    }
    echo '<td width="50%">
        <form name="reg" action="metro2.php" method="post">
            <b>Name:    </b>&nbsp;
            <input name="fname" maxlength="256" value=" ', $item->name , '" readonly style="width: 300px; border:0;" /><br>
            <img src="' . $item->image . '" alt="Product" height="200"><br>
            <b>Description:</b>&nbsp;' . $item->description . '<br>
            <b>Left:</b>&nbsp;

            <!-- New hidden field -->
            <input type="hidden" name="index" value="' . $index . '" />

            <input name="left" maxlength="7" value="' . $item->left . '" readonly style="width: 70px; border:0;" /><br>
            <label>
                <input type="submit" name="button" id="button" value="Reserve!" />
            </label>
        </form><br>
        <hr />
    </td>', PHP_EOL;

    $item_count++;
}
echo '</tr>
</table>';
?>

metro2.php:

<?php  
$products = simplexml_load_file("example.xml");

// Get the index of item from post request
$index = intval($_POST['index']);

$fname = $_POST['fname'];

// Parse the left value to in an integer
$left = intval($_POST['left']);
$new_left = $left - 1;
echo 'You want to reserve&nbsp;<b>', $fname, '</b>.<br />';
echo 'There are now only&nbsp;<b>', $new_left, '</b>&nbsp;of this product.';

// Select the correct item which by index and set new value
// Use the children method and not the item attribute for select the item,
$products->children()[$index]->left = $new_left;

$products->asXML("example.xml");
?>

I make also some HTML changes.

EDIT #2:

If you don't understand the foreach statement correctly look here.

EDIT #3:

Changed the type of loop and the selection of item from object $products to get the item by index.