预定义常量

下列常量由此扩展定义,且仅在此扩展编译入 PHP 或在运行时动态载入时可用。

LIBXML_BIGLINES (integer)
Allows line numbers greater than 65535 to be reported correctly.

Note:

Only available as of PHP 7.0.0 with Libxml >= 2.9.0

LIBXML_COMPACT (integer)
Activate small nodes allocation optimization. This may speed up your application without needing to change the code.

Note:

Only available in Libxml >= 2.6.21

LIBXML_DTDATTR (integer)
Default DTD attributes
LIBXML_DTDLOAD (integer)
Load the external subset
LIBXML_DTDVALID (integer)
Validate with the DTD
LIBXML_HTML_NOIMPLIED (integer)
Sets HTML_PARSE_NOIMPLIED flag, which turns off the automatic adding of implied html/body... elements.

Note:

Only available in Libxml >= 2.7.7 (as of PHP >= 5.4.0)

LIBXML_HTML_NODEFDTD (integer)
Sets HTML_PARSE_NODEFDTD flag, which prevents a default doctype being added when one is not found.

Note:

Only available in Libxml >= 2.7.8 (as of PHP >= 5.4.0)

LIBXML_NOBLANKS (integer)
Remove blank nodes
LIBXML_NOCDATA (integer)
Merge CDATA as text nodes
LIBXML_NOEMPTYTAG (integer)
Expand empty tags (e.g. <br/> to <br></br>)

Note:

This option is currently just available in the DOMDocument::save and DOMDocument::saveXML functions.

LIBXML_NOENT (integer)
Substitute entities
LIBXML_NOERROR (integer)
Suppress error reports
LIBXML_NONET (integer)
Disable network access when loading documents
LIBXML_NOWARNING (integer)
Suppress warning reports
LIBXML_NOXMLDECL (integer)
Drop the XML declaration when saving a document

Note:

Only available in Libxml >= 2.6.21

LIBXML_NSCLEAN (integer)
Remove redundant namespace declarations
LIBXML_PARSEHUGE (integer)
Sets XML_PARSE_HUGE flag, which relaxes any hardcoded limit from the parser. This affects limits like maximum depth of a document or the entity recursion, as well as limits of the size of text nodes.

Note:

Only available in Libxml >= 2.7.0 (as of PHP >= 5.3.2 and PHP >= 5.2.12)

LIBXML_PEDANTIC (integer)
Sets XML_PARSE_PEDANTIC flag, which enables pedantic error reporting.

Note:

Available as of PHP >= 5.4.0

LIBXML_XINCLUDE (integer)
Implement XInclude substitution
LIBXML_ERR_ERROR (integer)
A recoverable error
LIBXML_ERR_FATAL (integer)
A fatal error
LIBXML_ERR_NONE (integer)
No errors
LIBXML_ERR_WARNING (integer)
A simple warning
LIBXML_VERSION (integer)
libxml version like 20605 or 20617
LIBXML_DOTTED_VERSION (string)
libxml version like 2.6.5 or 2.6.17
LIBXML_SCHEMA_CREATE (integer)
Create default/fixed value nodes during XSD schema validation

Note:

Only available in Libxml >= 2.6.14 (as of PHP >= 5.5.2)

User Contributed Notes

vetalstar at mail dot ru 16-Nov-2017 12:26
LIBXML_DOTTED_VERSION option doesn't work.
libxml version: 2.9.4

<?php

echo LIBXML_DOTTED_VERSION;
$xml = new SimpleXMLElement('<fasa_request id="1234567"/>', LIBXML_NOXMLDECL);

?>
@oneseventeen 05-Feb-2011 11:51
When inserting XML DOM Elements inside existing XML DOM Elements that I loaded from an XML file using the following code, none of my new elements were formatted correctly, they just showed up on one line:

<?php
$dom
= DOMDocument::load('file.xml');
$dom->formatOutput = true;
//$dom->add some new elements with child nodes somewhere inside the loaded XML using insertBefore();
$dom->saveXML();
//output: everything looks normal but the new nodes are all on one line.
?>

I found I could pass LIBXML_NOBLANKS to the load method and it would reformat the whole document, including my added stuff:
<?php
$dom
= DOMDocument::load('file.xml', LIBXML_NOBLANKS);
$dom->formatOutput = true;
//$dom->add some new elements with child nodes somewhere inside the loaded XML using insertBefore();
$dom->saveXML();
//output: everything looks newly formatted, including new nodes
?>

Hope this helps, took me hours of trial and error to figure this out!
zachatwork at gmail dot com 09-Feb-2010 11:30
Note: The LIBXML_NOXMLDECL constant is defined in this library but is not supported by DOMDocument (yet).

See also: http://bugs.php.net/bug.php?id=47137

<?php

print "PHP_VERSION:      ".PHP_VERSION."\n";
print
"LIBXML_VERSION:   ".LIBXML_VERSION."\n";
print
"LIBXML_NOXMLDECL: ".LIBXML_NOXMLDECL."\n";

$dom = new DomDocument();
$dom->loadXML("<foo />");

# This should work but doesn't.

print "DOMDocument doesn't honor LIBXML_NOXMLDECL:\n";
print
$dom->saveXML(null,LIBXML_NOXMLDECL);

# This works, and will still work after the above is fixed.

print "Forwards compatible workaround:\n";
$lines = explode("\n", $dom->saveXML(null, LIBXML_NOXMLDECL), 2);
if(!
preg_match('/^\<\?xml/', $lines[0]))
    print
$lines[0];
print
$lines[1];

?>

PHP_VERSION:      5.3.1-0.dotdeb.1
LIBXML_VERSION:   20632
LIBXML_NOXMLDECL: 2
DOMDocument doesn't honor LIBXML_NOXMLDECL:
<?xml version="1.0"?>
<foo/>
Forwards compatible workaround:
<foo/>