Question

So my problem is that when I’m editing an XML file (below) with some PHP lines, everything works the first time, and then it deletes false lines and creates the new ones in the wrong places.

Here the PHP script for deleting the rows:

<?php
session_start(); 

// The file
$filePath = '/....../test/test.xml';

// Grab file into an array, by lines
$fileArr = file($filePath);

// Remove desired line
unset($fileArr[7]); // $fileArr[15] == line #16
unset($fileArr[16]); // idem
unset($fileArr[25]); // idem

//Put back with PHP5
file_put_contents($filePath, implode('', $fileArr ));

session_destroy(); 
?>

Here the PHP script to write new rows

<?php
session_start(); 

// The file
$filePath = '/....../test/test.xml';

// Grab file into an array, by lines
$fileArr = file($filePath);

//Change
$etichettaasse = "\t\t\t\t<string>\t14 gen</string>\n\r";
$medianord =  "\t\t\t\t<number>\t280\t</number>\n\r";
$mediasud =  "\t\t\t\t<number>\t280\t</number>\n\r";

// Replace line
$fileArr[11] = $etichettaasse;
$fileArr[19] = $medianord;
$fileArr[27] = $mediasud;

// Implode and save
file_put_contents($filePath, implode('', $fileArr ));

session_destroy(); 
?>

Here the original XML:

<chart>
<axis_category color='ffffff' skip='0' size='12' alpha='80' />
<axis_value color='ffffff' skip='10' size='12' show_min='false' min="80" max="130"  />
<chart_border top_thickness='1' bottom_thickness='1' left_thickness='1' right_thickness='1' />              
<chart_data>
    <row>
        <null/>
            <string>    3 dic</string>
            <string>    10 dic</string>
            <string>    17 dic</string>
            <string>    24 dic</string>
            <string>    31 dic</string>

    </row>
    <row>
        <string>Media Nord</string>
            <number>    102.72  </number>
            <number>    101.60  </number>
            <number>    101.85  </number>
            <number>    101.84  </number>
            <number>    101.84  </number>

    </row>
    <row>
        <string>Media Sud</string>
            <number>    102.28  </number>
            <number>    101.24  </number>
            <number>    101.70  </number>
            <number>    101.88  </number>
            <number>    101.88  </number>

    </row>
</chart_data>
</chart>

After the first round of PHP script, it is updated as requested:

<chart>
<axis_category color='ffffff' skip='0' size='12' alpha='80' />
<axis_value color='ffffff' skip='10' size='12' show_min='false' min="80" max="130"  />
<chart_border top_thickness='1' bottom_thickness='1' left_thickness='1' right_thickness='1' />              
<chart_data>
    <row>
        <null/>
            <string>    10 dic</string>
            <string>    17 dic</string>
            <string>    24 dic</string>
            <string>    31 dic</string>
            <string>    14 gen</string>

    </row>
    <row>
        <string>Media Nord</string>
            <number>    101.60  </number>
            <number>    101.85  </number>
            <number>    101.84  </number>
            <number>    101.84  </number>
            <number>    280 </number>

    </row>
    <row>
        <string>Media Sud</string>
            <number>    101.24  </number>
            <number>    101.70  </number>
            <number>    101.88  </number>
            <number>    101.88  </number>
            <number>    280 </number>

    </row>
</chart_data>

After the second round of the PHP script:

<chart>
<axis_category color='ffffff' skip='0' size='12' alpha='80' />
<axis_value color='ffffff' skip='10' size='12' show_min='false' min="80" max="130"  />
<chart_border top_thickness='1' bottom_thickness='1' left_thickness='1' right_thickness='1' />              
<chart_data>
    <row>
        <null/>
            <string>    17 dic</string>
            <string>    24 dic</string>
            <string>    14 gen</string>
            <string>    14 gen</string>

    </row>
    <row>
        <string>Media Nord</string>
            <number>    101.60  </number>
            <number>    101.84  </number>
            <number>    280 </number>


            <number>    280 </number>

    <row>
        <string>Media Sud</string>
            <number>    101.24  </number>
            <number>    101.70  </number>
            <number>    280 </number>


    </row>
            <number>    280 </number>

I’d also be happy if I could have only one PHP file instead of 2, but I have no idea how to do that.

Is this the best way to modify this XML file, or is there another way?

Notice that the new line that will be written to HTML from a user.

I have this “start” script for deleting the content I want to delete.

What do you think of it?

<?php
$file = '/...../test.xml';


$fp = fopen(file,"w"); // open it for WRITING ("w")

if (flock($fp, LOCK_EX)) {

    //do actions here
    $xml = file_get_contents($file);
    $sxe = simplexml_load_string($xml);

    echo '<pre>';

    // "delete the 1th string of row 1, etc."
    unset($sxe->chart_data->row[0]->string[0]);
    unset($sxe->chart_data->row[1]->number[0]);
    unset($sxe->chart_data->row[2]->number[0]);

    $sxe->chart_data->row[0]->addChild('string', 'test');
    $sxe->chart_data->row[1]->addChild('number', '999');
    $sxe->chart_data->row[2]->addChild('number', '9999');

    file_put_contents($file, $sxe->asXML());


    // unlock the file
    flock($fp, LOCK_UN);

} else {

    // flock() returned false, no lock obtained
    print "Could not lock $file!\n";
}

?>

Answer 1

The problem is when you unset() an array member you change the line numbers. This is easy to demonstrate:

$origfile = array(
    "line1\n",
    "line2\n",
    "line3\n",
);

unset($file[1]); // delete line 2

$round1file = implode('', $file); // "write the file"

The result is a two-line file, not a three-line file!

line1
line3

So when you read it in again, your array will look like this:

$round1file = array("line1\n","line3\n");

If you delete line 2 again, you will obviously be left with array("line1\n")

The immediate solution is to replace the line with a blank line rather than to unset the array member, i.e. $fileArr[7] = "\n" instead of unset($fileArr[7]).

However, what you are doing is completely insane. This is an XML file, so you need to parse and write it with an XML library or I guarantee you you will end up with invalid XML sooner or later! Also, you cannot safely write over a file that multiple processes may be using–you need to use some sort of file locking or a proper database.

For file locking, you can use a pair of functions like this:

function file_get_contents_locked($filename)
{
    $fp = fopen($filename, 'rb');
    if ($fp===FALSE) {
        throw new RuntimeException("Could not open file '{$filename}'");
    }
    if (flock($fp, LOCK_SH)) {
        $data = stream_get_contents($fp);
        flock($fp, LOCK_UN);
        fclose($fp);
        return $data;
    } else {
            fclose($fp);
        throw new RuntimeException("Could not acquire lock on file '{$filename}'");
    }
}


function file_put_contents_locked($filename, $data)
{
    return file_put_contents($filename, $data, LOCK_EX);
}

Or if you are on a *nix of some kind where renames are atomic, you can write to a temporary file and rename over the old file instead of using locking. (You don’t need locking in this case because the file will never be half-read or half-written as long as you write using this method.)

function write_atomic($fullfilename, $data) {
    $tmpname = tempnam(dirname($fullfilename), 'write_atomic-');
    if (FALSE!==file_put_contents($tmpname, $data)) {
        rename($tmpname, $fillfilename);
    }
    unlink($tmpname);
}

For the XML manipulation, two easy options are SimpleXML which is simpler but less powerful, and DOMDocument which is more complex but more powerful. (You can also use XMLReader and XMLWriter, but these are much harder to use and much slower–they are only needed if you can’t fit your entire XML file in memory at once.)

Here is an example to get you started. Look at the linked documentation for more details:

function delete_xml_stuff($filename)
{
    $xml = file_get_contents_locked($filename);
    $sxe = simplexml_load_string($xml);
    // e.g., "delete the 2th string of row 1"
    unset($sxe->chart_data->row[0]->string[1]);
    file_put_contents_locked($filename, $sxe->asXML());

    // if you have more complex criteria, use DOMDocument:

    $d = new DOMDocument();
    $d->loadXML($xml);
    $xp = new DOMXPath($d);
    $results = $xp->query('//chart_data/row[2]/*[3]');
    if ($results->length) {
        $row2column3 = $results->item(0);
        $row2column3->parentNode->removeChild($row2column3);
    }
    file_put_contents_locked($d->saveXML());
}