simplexml_load_string and simplexml_load_file are buggy and don't work well on XML with a complex markup. I tried both functions to parse some VALID XML SOAP responses and could not even get an error message. I had to use DOMDocument instead (worked like a charm).

Here is how we suppose to check simplexml for errors (if you are lucky to see errors, not just "false" returned from function)

libxml_use_internal_errors(true);
$xml=simplexml_load_string($myXMLData); //or simplexml_load_file

foreach( libxml_get_errors() as $error ) {

    print_r($error);

}

For PHP 7 and Ubuntu 14.04 the procedure is follows. Since PHP 7 is not in the official Ubuntu PPAs you likely installed it through Ondřej Surý's PPA (sudo add-apt-repository ppa:ondrej/php). Go to /etc/php/7.0/fpm and edit php.ini, uncomment to following line:

extension=php_xmlrpc.dll

Then simply install php7.0-xml:

sudo apt-get install php7.0-xml

And restart PHP:

sudo service php7.0-fpm restart

And restart Apache:

sudo service apache2 restart

If you are on a later Ubuntu version where PHP 7 is included, the procedure is most likely the same as well (except adding any 3rd party repository).

According to the manual simplexml_load_string has the following parameters:

SimpleXMLElement simplexml_load_string ( string $data [, string $class_name = "SimpleXMLElement" [, int $options = 0 [, string $ns = "" [, bool $is_prefix = false ]]]] )

Therefore, I believe that you can load your XML this way :

simplexml_load_string($var, "SimpleXMLElement", 0, "epp", true);

I hope this works for you.

This errors means you do not have the simpleXML library loaded with PHP.

You should print your phpinfo() in Command Line mode and check the presence of the simplexml library.

Check then how to install the simplexml library on your OS.

To answer your question, let's first examine the problem.

Problem

Assuming you are displaying the contents of your $xml variable through:

php > print_r($xml);

Here, you are listing the children of the current node (the root node) with the default namespace (without prefix) which is not declared in that node:

 <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://www.beautyfort.com/api/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

If you would list the namespaces of that node:

php > print_r($xml->getNamespaces());
Array
(
    [SOAP-ENV] => http://schemas.xmlsoap.org/soap/envelope/
)

there is only a single one visible, because that is the only one actually used in that (root) node excluding its children.

To list all used namespaces of the root and all its children add 'true' as first argument:

php > print_r($xml->getNamespaces(true));
Array
(
    [SOAP-ENV] => http://schemas.xmlsoap.org/soap/envelope/
    [ns1] => http://www.beautyfort.com/api/
    [xsi] => http://www.w3.org/2001/XMLSchema-instance
)

To list all declared namespaces of the root and all its children:

php > print_r($xml->getDocNamespaces(true));
Array
(
    [SOAP-ENV] => http://schemas.xmlsoap.org/soap/envelope/
    [ns1] => http://www.beautyfort.com/api/
    [xsi] => http://www.w3.org/2001/XMLSchema-instance
)

Solution #1

simplexml_load_string allows to set a default namespace as argument, e.g. SOAP-ENV (with extra argument to indicate that it is a prefix):

php > $xml = simplexml_load_string($content, "SimpleXMLElement", 0, "SOAP-ENV", true);

If you now print your variable, you will get closer to what you need:

php > print_r($xml);
SimpleXMLElement Object
(
    [Body] => SimpleXMLElement Object
        (
        )

)

But this only holds for the root node.

When listing children, you still need to specify a namespace if the children use namespaces other than the default (empty) one, and indicate whether its a prefix or namespace:

php > print_r($xml->children("SOAP-ENV", true));
SimpleXMLElement Object
(
    [Body] => SimpleXMLElement Object
        (
        )

)

To see the children of the first root child do the following:

php > print_r($xml->children("SOAP-ENV", true)->children("ns1", true));
SimpleXMLElement Object
(
    [ProductSearchResponse] => SimpleXMLElement Object
        (
            ...
        )

)

But this might not be what you are looking for, as it is not a generic solution.

Solution #2

Use a string replace for all your namespaces and reload the XML document (stored in $content):

php > $content2 = str_replace(array_map(function($e) { return "$e:"; }, array_keys($xml->getDocNamespaces())), array(), $content);

Your input XML now looks like this:

php > echo $content2;
<?xml version="1.0" encoding="UTF-8"?><Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://www.beautyfort.com/api/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Body><ProductSearchResponse><TestMode>false</TestMode><Page>1</Page><ResultsPerPage>1</ResultsPerPage><TotalResults>1276</TotalResults><Items><Item><StockCode>L3720</StockCode><Name>David Beckham Instinct Gift Set 30ml EDT + 150ml Shower Gel</Name><QuantityAvailable>1</QuantityAvailable><UnitPrice Currency="GBP"><Amount>8.72</Amount></UnitPrice><YourRating nil="true"/><YourStockCode></YourStockCode><ImageLastUpdated>2016-12-22 18:13:08</ImageLastUpdated><ThumbnailImageUrl>https://www.beautyfort.com/pic/Y0NqeTBJbmdvaUx6ZUFOa0MyTlNObmhGckltYnVQQmg%3D</ThumbnailImageUrl><HighResImageUrl nil="true"/></Item></Items></ProductSearchResponse></Body></Envelope>

Reload and print:

php > $xml2 = simplexml_load_string($content2);
php > print_r($xml2);
SimpleXMLElement Object
(
    [Body] => SimpleXMLElement Object
        (
            [ProductSearchResponse] => SimpleXMLElement Object
                (
                    ...
                )

        )

)