CODEWITHSUNDEEP
phpxmlsorting
Wayne1079
Wayne1079

Reputation: 1

Sort XML data by element in php

I am very new to coding and I have some practise exercises by my college and the first is to take an XML document and return the data using php which I have managed to do however the next step is to sort that data by either a new child element called 'note_id' or by adding an 'id' attribute to the note element and then show the data in descending order. I went with adding a new child element of note_id and I have inserted note_id number 6 in the middle of the other elements to see if it would sort.

I have tried numerous things by looking up information on the internet however I feel like I am just going round in circles as I am new to this and nothing seems to work (obviously as I don't know what I am doing - but got to start somewhere).

I haven't posted this question just to get an answer, I also need to understand how and why this method works if someone does reply with an answer.

My XML data is shown below and is stored in a file called 'note.xml'.

    <?xml version="1.0" encoding="UTF-8"?>
<notes>
<note>
<note_id>1</note_id>
<to>tove1</to>
<from>Jani1</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

<note>
<note_id>2</note_id>
<to>tove2</to>
<from>Jani2</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

<note>
<note_id>3</note_id>
<to>tove3</to>
<from>Jani3</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

<note>
<note_id>6</note_id>
<to>tove6</to>
<from>Jani6</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

<note>
<note_id>4</note_id>
<to>tove4</to>
<from>Jani4</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

<note>
<note_id>5</note_id>
<to>tove5</to>
<from>Jani5</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

</notes>

My current PHP code is below which brings back the XML.

?php
// Loads the xml file.
$xml= simplexml_load_file("note.xml");
// Returns the top level xml element - notes.
echo $xml->getName() . "<br />";


// Returns each note element.
foreach($xml->note as $note){
     echo $note->getName() . ": " . $note . "<br />";
// Returns each child element of note element.
    foreach($note->children() as $child){
        echo $child->getName() . ": " . $child . "<br />";

    }

    echo "<br />";
}


echo "<br />";


?>

Upvotes: 0

Views: 1171

Answers (1)

The fourth bird
The fourth bird

Reputation: 163632

This is an example of how you could do it:

  • Load the note.xml file. In this case I have used a custom Note class which will load the file by passing it to the constructor.
  • You want to sort the xml by 'note_id'. To do this, you could convert the xml to an array of arrays where the arrays are essentially the notes.

  • Now that you have an array of arrays, you can sort these using the php native usort function:

  • Then, you can generate new xml based on the sorted array of arrays.

Example:

<?php
class Note
{
    /**
     * @var array
     */
    private $notes = [];

    /**
     * @param $fileName
     */
    public function __construct($fileName)
    {
        $xml = simplexml_load_file($fileName);
        $this->simpleXMLElementToArray($xml);
    }

    /**
     * Convert the SimpleXMLElement to array format.
     *
     * @param SimpleXMLElement $xml
     */
    protected function simpleXMLElementToArray(SimpleXMLElement $xml)
    {
        // For each note, create an associative array and add it to the $notes array
        foreach ($xml->note as $note) {
            $this->notes[] = json_decode(json_encode($note), true);
        }
    }

    /**
     * Sort the internal $notes array using usort.
     *
     * http://php.net/manual/en/function.usort.php
     */
    public function sortByNoteIdDescending()
    {
        usort($this->notes, array('Note', 'sortNotesArrayByNoteIdDescending'));
    }

    /**
     * Custom function to sort by note_id.
     *
     * @param array $note1
     * @param array $note2
     * @return int
     */
    protected function sortNotesArrayByNoteIdDescending(array $note1, array $note2)
    {
        if ($note1['note_id'] == $note2['note_id']) {
            return 0;
        } else if ($note1['note_id'] < $note2['note_id']) {
            return 1;
        } else {
            return -1;
        }
    }

    /**
     * Generate xml from the internal $notes array.
     */
    public function toXml()
    {
        $xml = new SimpleXMLElement('<notes/>');

        foreach ($this->notes as $note ) {
            $noteElement = $xml->addChild('note');
            $noteElement->addChild("note_id", $note["note_id"]);
            $noteElement->addChild("to", $note["to"]);
            $noteElement->addChild("from", $note["from"]);
            $noteElement->addChild("body", $note["body"]);
        }

        // To generate a nice output format
        $dom = dom_import_simplexml($xml)->ownerDocument;
        $dom->formatOutput = true;

        return $dom->saveXML();
    }
}

$note = new Note('note.xml');
$note->sortByNoteIdDescending();
echo $note->toXml();

Upvotes: 1

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