Use xml_parser_get_option to check the character encoding settings of the XML parser

Introduction to xml_parser_get_option()

xml_parser_get_option() is used to get the settings for a specific XML parser. The function prototype is as follows:

 mixed xml_parser_get_option(resource $parser, int $option)

where $parser is a parser resource created by xml_parser_create() or related functions, and $option is the option constant you want to obtain, such as XML_OPTION_TARGET_ENCODING , XML_OPTION_CASE_FOLDING , etc.

If the setting item exists, the function returns its current value; otherwise, it returns false .

Common options explanation

For coding related, the most commonly used options are:

 XML_OPTION_TARGET_ENCODING

This option represents the target encoding of the parser output, which determines how the parser converts internal characters represented as strings available in PHP. The default value is "UTF-8" , or "ISO-8859-1" or "US-ASCII" .

Note 1: Understand the difference between target encoding and source encoding

xml_parser_get_option() returns the target encoding , that is, the encoding of the parser output result, rather than the encoding of the original XML file. The encoding of the original XML file is determined by the XML declaration, for example:

 <?xml version="1.0" encoding="ISO-8859-1"?>

Even if the XML declaration is ISO-8859-1, xml_parser_get_option() will return "UTF-8" as long as you do not manually change the parser settings, because PHP will automatically convert the source content to the target encoding.

Note 2: The corresponding relationship between setting and obtaining

If you plan to modify the default target encoding, you can use xml_parser_set_option() :

 $parser = xml_parser_create();
xml_parser_set_option($parser, XML_OPTION_TARGET_ENCODING, "ISO-8859-1");

Then use xml_parser_get_option() to verify whether the setting is successful:

 $encoding = xml_parser_get_option($parser, XML_OPTION_TARGET_ENCODING);
echo "Current encoding：$encoding";

Please note that arbitrary encoding is not supported, setting an unsupported encoding will cause the parser to fail.

Note 3: Inconsistent file flow and encoding may cause errors

If the read XML file itself uses a character set that is inconsistent with the target encoding and contains non-ASCII characters, the PHP parser may throw an error because the characters cannot be mapped. Therefore, it is very critical to ensure that the actual encoding of the source file is consistent with the declaration and compatible with the target encoding.

The original encoding of the file can be detected through mb_detect_encoding() , and if necessary, use mb_convert_encoding() to convert it into the target encoding:

 $xml = file_get_contents("https://gitbox.net/data/sample.xml");
$xml = mb_convert_encoding($xml, "UTF-8", "auto");
$parser = xml_parser_create("UTF-8");
xml_parse($parser, $xml, true);

Note 4: Distinguish the parser instance

Each parser instance is independent. When obtaining settings, make sure that you pass in the correct parser resource . This is especially important when working with multiple XML files simultaneously or encapsulating parser logic in a class.

Note 5: No direct relationship with libxml extension

xml_parser_get_option() belongs to the Expat parser interface, not libxml-based DOM or SimpleXML, and therefore cannot be used for these extensions. It only works with SAX style parsers created with xml_parser_create() .