difference between getDocNamespaces and getNamespaces in SimpleXML

问题

Two method of SimpleXMLElement are getDocNamespaces and getNamespaces. Both seems same to me, i tried the example of each other changing the method name but same result.

So can anyone explain it to me, what is the difference? Links from php.net getNamespaces getdocnamespaces

回答1:

getDocNamespaces() returns all namespaces declared in document; getNamespaces() returns only those namespaces that are actually used in the document.

Example #1 in the getNamespaces() doc page shows this with xmlns:t="http://example.org/test" defined, but not used.

回答2:

Actually those methods do two similar but different things. Both retrieve namespaces. Both can even do that recursively. Both can operate on elements.

The difference is to obtain namespaces used (###:element) with/on specific elements or defined (xmlns:###="XMLNS-URI") on specific elements.

Some examples:

getNamespaces obtains used namespaces. E.g. if you've got a person element somewhere in the tree like:

...
   <p:person t:id="1">John Doe</p:person>
...

And you use

$sxe->person[0]->getNamespaces(TRUE);

on it, it will give you two namespaces, those two used on that element:

[p] => http://example.org/ns
[t] => http://example.org/test

getDocNamespaces in difference, when operating on that same element will give you the namespaces defined:

$sxe->person[0]->getDocNamespaces(TRUE, FALSE);

As that element does not define any, the array is empty.

In difference to that, on a different, second person element:

...
    <p:person t:id="2" a:addr="123 Street" xmlns:a="http://example.org/addr">
        Susie Q. Public
    </p:person>
...

$sxe->person[1]->getDocNamespaces(TRUE, FALSE);

will give you exactly one namespace because it's defined there:

[a] => http://example.org/addr

This should clarfiy it. You can permutate a bit through the diverse parameter combos, so here is some example script (Demo):

<?php
/**
 * @link https://stackoverflow.com/a/18354621/367456
 */

$xml = <<<XML
<?xml version="1.0" standalone="yes"?>
<people xmlns:p="http://example.org/ns" xmlns:t="http://example.org/test">
    <p:person t:id="1">John Doe</p:person>
    <p:person t:id="2" a:addr="123 Street" xmlns:a="http://example.org/addr">
        Susie Q. Public
    </p:person>
</people>
XML;

$sxe = new SimpleXMLElement($xml, 0, FALSE, 'http://example.org/ns');

echo 'person[0]->getNamespaces(TRUE): ', 
!print_r($sxe->person[0]->getNamespaces(TRUE)), "\n";

echo 'person[0]->getNamespaces(FALSE): ', 
!print_r($sxe->person[0]->getNamespaces(FALSE)), "\n";

echo 'person[0]->getDocNamespaces(TRUE): ', 
!print_r($sxe->person[0]->getDocNamespaces(TRUE)), "\n";

echo 'person[0]->getDocNamespaces(TRUE, FALSE): ', 
!print_r($sxe->person[0]->getDocNamespaces(TRUE, FALSE)), "\n";

echo 'person[1]->getDocNamespaces(TRUE, FALSE): ', 
!print_r($sxe->person[1]->getDocNamespaces(TRUE, FALSE)), "\n";

echo 'sxe->getNamespaces(FALSE): ', 
!print_r($sxe->getNamespaces(FALSE)), "\n";

echo 'sxe->getDocNamespaces(TRUE, FALSE): ', 
!print_r($sxe->getDocNamespaces(TRUE, FALSE)), "\n";

echo 'sxe->getDocNamespaces(FALSE, FALSE): ', 
!print_r($sxe->getDocNamespaces(FALSE, FALSE)), "\n";

echo 'sxe->getNamespaces(TRUE): ', 
!print_r($sxe->getNamespaces(TRUE)), "\n";

echo 'sxe->getDocNamespaces(TRUE): ', 
!print_r($sxe->getDocNamespaces(TRUE)), "\n";

Output:

person[0]->getNamespaces(TRUE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
)

person[0]->getNamespaces(FALSE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
)

person[0]->getDocNamespaces(TRUE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
    [a] => http://example.org/addr
)

person[0]->getDocNamespaces(TRUE, FALSE): Array
(
)

person[1]->getDocNamespaces(TRUE, FALSE): Array
(
    [a] => http://example.org/addr
)

sxe->getNamespaces(FALSE): Array
(
)

sxe->getDocNamespaces(TRUE, FALSE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
    [a] => http://example.org/addr
)

sxe->getDocNamespaces(FALSE, FALSE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
)

sxe->getNamespaces(TRUE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
    [a] => http://example.org/addr
)

sxe->getDocNamespaces(TRUE): Array
(
    [p] => http://example.org/ns
    [t] => http://example.org/test
    [a] => http://example.org/addr
)

---

See as well:

• What are the “$ns” and “$is_prefix” parameters about?

来源：https://stackoverflow.com/questions/18351002/difference-between-getdocnamespaces-and-getnamespaces-in-simplexml