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SimpleXMLElement::__construct

(PHP 5, PHP 7)

SimpleXMLElement::__construct — Creates a new SimpleXMLElement object

说明

final public SimpleXMLElement::__construct ( string $data [, int $options = 0 [, bool $data_is_url = FALSE [, string $ns = "" [, bool $is_prefix = FALSE ]]]] )

Creates a new SimpleXMLElement object.

参数

data: A well-formed XML string or the path or URL to an XML document if data_is_url is TRUE.
options: Optionally used to specify additional Libxml parameters.

Note:
It may be necessary to pass LIBXML_PARSEHUGE to be able to process deeply nested XML or very large text nodes.
data_is_url: By default, data_is_url is FALSE. Use TRUE to specify that data is a path or URL to an XML document instead of string data.
ns: Namespace prefix or URI.
is_prefix: TRUE if ns is a prefix, FALSE if it's a URI; defaults to FALSE.

返回值

Returns a SimpleXMLElement object representing data.

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.

Tip

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

范例

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

Example #1 Create a SimpleXMLElement object


<?php

include 'example.php';

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

?>

以上例程会输出：

PHP: Behind the Parser

Example #2 Create a SimpleXMLElement object from a URL


<?php

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

?>

更新日志

版本	说明
5.2.0	Added the `ns` and `is_prefix` parameters.
5.1.2	Added the `options` and `data_is_url` parameters.

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

User Contributed Notes

rowan dot collins at gmail dot com 22-Apr-2017 03:23


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

ahmad dot mayahi at gmail dot com 07-Jun-2016 09:36


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);

Phil Cross 01-Sep-2014 11:39


It's worth noting, that you need to typecast dynamic property names to string in order to retrieve there value, for example:



<?php 

    $xml = new SimpleXMLElement('records.xml', 0, true);



    // This will work as expected because its a hard coded property value

    foreach($xml as $record){

        echo $record->id;    // Will output the ID fine

    }



    // Dynamic properties require typecasting to string

    $xml_field = 'id';

    foreach($xml as $record){



        // This will dump a SimpleXMLElement object

        var_dump($record->$xml_field);



        // This will output the value as expected

        echo (string)$record->$xml_field;

    }

?>

bertolini dot cedric at me dot com 16-Jun-2014 11:07


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.

kumarldh at gmail dot com 22-Mar-2011 10:50


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();


}


?>

uramihsayibok, gmail, com 16-Aug-2009 06:52


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.

tudor at culise dot net 20-Nov-2007 03:35


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.