SimpleXMLElement::__construct

(PHP 5, PHP 7, PHP 8)

SimpleXMLElement::__construct — Creates a new SimpleXMLElement object

说明

public SimpleXMLElement::__construct(
    string $data,
    int $options = 0,
    bool $dataIsURL = false,
    string $namespaceOrPrefix = "",
    bool $isPrefix = false
)

Creates a new SimpleXMLElement object.

参数

data: A well-formed XML string or the path or URL to an XML document if dataIsURL is true.
options: Optionally used to specify additional Libxml parameters, which affect reading of XML documents. Options which affect the output of XML documents (e.g. LIBXML_NOEMPTYTAG) are silently ignored.

注意:
It may be necessary to pass LIBXML_PARSEHUGE to be able to process deeply nested XML or very large text nodes.
dataIsURL: By default, dataIsURL is false. Use true to specify that data is a path or URL to an XML document instead of string data.
namespaceOrPrefix: Namespace prefix or URI.
isPrefix: true if namespaceOrPrefix is a prefix, false if it's a URI; defaults to false.

错误／异常

Produces an E_WARNING error message for each error found in the XML data and additionally throws an Exception if the XML data could not be parsed.

小技巧

Use libxml_use_internal_errors() to suppress all XML errors, and libxml_get_errors() to iterate over them afterwards.

示例

注意:
Listed examples may include example.php, which refers to the XML string found in the first example of the basic usage guide.

示例 #1 Create a SimpleXMLElement object

<?php

include 'example.php';

$sxe = new SimpleXMLElement($xmlstr);
echo $sxe->movie[0]->title;

?>

以上示例会输出：

PHP: Behind the Parser

示例 #2 Create a SimpleXMLElement object from a URL

<?php

$sxe = new SimpleXMLElement('http://example.org/document.xml', 0, true);
echo $sxe->asXML();

?>

参见

Basic SimpleXML usage
simplexml_load_string() - Interprets a string of XML into an object
simplexml_load_file() - Interprets an XML file into an object
Dealing with XML errors
libxml_use_internal_errors() - Disable libxml errors and allow user to fetch error information as needed
libxml_set_streams_context() - Set the streams context for the next libxml document load or write

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用户贡献的备注 7 notes

down

rowan dot collins at gmail dot com ¶

7 years ago

The manual doesn't really explain what the $ns argument (and the accompanying $is_prefix) are for.

What they do is similar to the ->children() method: they set the context of the returned object to that namespace, so that access via ->elementName and ['attributeName'] refer to elements and attributes in that namespace.

In particular, they do *not* change the namespaces which exist on the document.

See this example:

<?php
// This XML contains two elements called <child>
// One is in the namespace http://example.com, with local prefix 'ws'
// The other has no namespace (no prefix, and no default namespace declared)
$xml = '<ws:example xmlns:ws="http://example.com"><child>Not in namespace</child><ws:child>In example namespace</ws:child></ws:example>';

$sx0 = new SimpleXMLElement($xml, 0, false);
$sx1 = new SimpleXMLElement($xml, 0, false, 'http://example.com');
$sx2 = new SimpleXMLElement($xml, 0, false, 'ws', true);

echo "
    Without: {$sx0->child}
    By namespace: {$sx1->child}
    By prefix: {$sx2->child}
";
?>

Output:

 Without: Not in namespace
 By namespace: In example namespace
 By prefix: In example namespace

down

tudor at culise dot net ¶

17 years ago

This class is extendable, but it's too bad that its constructor cannot be overriden (PHP says it's a final method). Thus the class should be wrapped using the delegation principle rather that extended.

down

ahmad dot mayahi at gmail dot com ¶

8 years ago

You won't be able to load an XML file without root element:

//This will throw an exception
$xml = new SimpleXMLElement('<?xml version="1.0" encoding="UTF-8"?>', null, false);

//Here is the solution
$xml = new SimpleXMLElement('<?xml version="1.0" encoding="UTF-8"?><root></root>', null, false);

down

info at ensostudio dot ru ¶

3 years ago

Extended SimpleXMLElement:
<?php
class XmlElement extends \SimpleXMLElement
{
    public static function factory(string $root): self
    {
        return new static('<?xml version="1.0" encoding="UTF-8"?><'.$root.'/>', LIBXML_BIGLINES | LIBXML_COMPACT);
    }

    /**
      * @param iterable $attributes An array of element attributes as name/value pairs
      * @return $this
      */
    public function addAttributes(iterable $attributes)
    {
        foreach ($attributes as $name => $value) {
            $this->addAttribute($name, $value);
        }

        return $this;
    }

    /**
      * @param string $name The sub-element name
      * @param string|array|null $valueOrAttributes The sub-element value or an array of attributes
      * @param string|null $namespace The sub-element namespace
      * @return static|null
      */
    public function addChild($name, $valueOrAttributes = null, $namespace = null)
    {
        if (is_array($valueOrAttributes)) {
            $child = parent::addChild($name, null, $namespace);
            foreach ($valueOrAttributes as $name => $value) {
                $child->addAttribute($name, $value);
            }
        } else {
            $child = parent::addChild($name, $valueOrAttributes, $namespace);
        }

        return $child;
    }

    /**
      * @param iterable $childs An array of sub-elements as name/value(or attributes) pairs
      * @return $this
      */
    public function addChilds(iterable $childs)
    {
        foreach ($childs as $name => $value) {
            $this->addChild($name, $value);
        }

        return $this;
    }
}
?>

down

bertolini dot cedric at me dot com ¶

10 years ago

It's worth noting that the behavior of SimpleXmlElement::__construct is not exactly the same as simplexml_load_string, regarding libxml_use_internal_errors().

In my case,

<?php
libxml_use_internal_errors(true);
new \SimpleXmlElement($data);
?>

was still throwing error. But as soon as I switched to 

<?php
libxml_use_internal_errors(true);
simplexml_load_string($data);
?>

everything worked fine and I stopped getting an error.

down

kumarldh at gmail dot com ¶

13 years ago

Using libxml_use_internal_errors() may suppress errors but Exception still requires decent handling. I used following code snippet.



<?php

libxml_use_internal_errors(true);

try{

    $xmlToObject = new SimpleXMLElement($notSoWellFormedXML);

} catch (Exception $e){

    echo 'Please try again later...';

    exit();

}

?>

down

uramihsayibok, gmail, com ¶

15 years ago

As I was filling out a bug report, I realized why (speculation here) the constructor is final: so that functions like simplexml_load_file and simplexml_load_string can work. I imagine the PHP-ized code looks something like



<?php



function simplexml_load_file($filename, $class_name = "SimpleXMLElement", $options = 0, $ns = "", $is_prefix = false) {

    return new $class_name($filename, $options, true, $ns, $is_prefix);

}



?>



If we were to use a different $class_name and change the constructor's definition these functions wouldn't work.



There's no easy, sensible solution that keeps simplexml_load_file and simplexml_load_string.