Include schema link into XML by using php - php

Question

I have a script in php which creates an XML file.
$xml1 = "<?xml version='1.0' encoding='utf-8'?>\n";
$xml1 .= "\t<invoices>\n";
$xml1 .= "\t\t<journal>\n";
I would need to add a schema link to "invoices" so that the XML output looks like the following:
<invoices xsi:noNamespaceSchemaLocation="http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd">
Whatever I try I always receive an error and the XML file is not created. How could I solve this or where could I find information on how to insert the required schema link correctly.
What I have tried so far is to add the link with different solutions including ' or "
$xml1 .= "\t<invoices xsi:noNamespaceSchemaLocation="http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd">\n";
$xml1 .= "\t<invoices 'xsi:noNamespaceSchemaLocation="http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd"'>\n";
Thank you
ADDON
The following error comes up when opening the created file with your solution:
$xml1 .= "\t<invoices xsi:noNamespaceSchemaLocation=\"http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd\">\n";
XML Parsing Error: prefix not bound to a namespace
<invoices xsi:noNamespaceSchemaLocation="http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd">
--------^
SOLUTION:
The following code was the solution for me:
$xml1 = "<?xml version='1.0' encoding='utf-8'?>\n";
$xml1 .= "\t<invoices xmlns='http://www.w3schools.com' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:noNamespaceSchemaLocation='http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd'>\n";
$xml1 .= "\t\t<journal>\n";

Answer 1

Do not try to create xml's through string concatenation. You will have a hard time doing this. Use a designated php api for creating xml documents.
Here is a minimal example that will create a invoices.xml.
/* create a dom document with encoding utf8 */
$domtree = new DOMDocument('1.0', 'UTF-8');
/* create the root element of the xml tree */
$xmlRoot = $domtree->createElement("xml");
/* append it to the document created */
$xmlRoot = $domtree->appendChild($xmlRoot);
$invoices = $domtree->createElement("invoices");
$invoices->setAttribute('xsi:noNamespaceSchemaLocation', 'http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd');
$invoices = $xmlRoot->appendChild($invoices);
$journal = $domtree->createElement("journal");
$journal = $invoices->appendChild($journal);
$domtree->save("invoices.xml");
Content will be:
<?xml version="1.0" encoding="UTF-8"?>
<xml><invoices xsi:noNamespaceSchemaLocation="http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd"><journal/></invoices></xml>
Addon:
Based on your comment and post edit, I think you just need to quote the " in your string.
$xml1 .= "\t<invoices xsi:noNamespaceSchemaLocation=\"http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd\">\n";

Answer 2

The attribute like xsi:noNamespaceSchemaLocation uses a namespace prefix. Because of the prefix a assume that it is the namespace http://www.w3.org/2001/XMLSchema-instance.
Namespaces need to be defined, but they will be defined as necessary if you use the namespace aware methods of the DOM API. The end with the suffix NS.
$document = new DOMDocument();
$document->appendChild(
$document->createElement('invoices')
);
$document->documentElement->setAttributeNS(
// namespace
'http://www.w3.org/2001/XMLSchema-instance',
// attribute name including namespace prefix
'xsi:noNamespaceSchemaLocation',
// attribute value
'http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd'
);
$document->documentElement->appendChild(
$document->createElement('journal')
);
$document->formatOutput = TRUE;
Output:
<?xml version="1.0"?>
<invoices xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://schema.aptic.net/aptic-link-import-ledgeraccounts-v2.xsd">
<journal/>
</invoices>
You can see that the generated output includes a xmlns attribute that defines the nampespace used by the xsi prefix.
The XML view in the browsers hides the namespace definitions, often. Check the source to validate that it here.
You can generate the same XML uses string functions. If you do this keep in mind to escape values if needed.