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Use xml_parse and xml_get_errors to capture parsing errors

M66 2025-04-28

When processing XML data in PHP, the XML string can be parsed using the xml_parse function. However, XML files often have formatting problems, such as unclosed tags or character encoding errors, which can lead to parsing failures. To catch and handle these errors gracefully, we can use functions such as xml_parse , xml_get_error_code , xml_error_string , and xml_get_current_line_number .

Let's look at a complete example of how to use these functions to detect and report XML parsing errors.

Example: Capturing XML parsing errors

 <?php
// Simulate an error XML String（Missing closed tag）
$xmlData = <<<XML
<note>
    <to>user</to>
    <from>administrator</from>
    <heading>remind</heading>
    <body>This is a test message
</note>
XML;

// create XML Parser
$parser = xml_parser_create();

// 设置Parser选项
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0); // Keep label case
xml_parser_set_option($parser, XML_OPTION_SKIP_WHITE, 1);   // Ignore whitespace characters

// Try to parse XML data
if (!xml_parse($parser, $xmlData, true)) {
    $errorCode = xml_get_error_code($parser);
    $errorMessage = xml_error_string($errorCode);
    $lineNumber = xml_get_current_line_number($parser);
    
    echo "? Analysis XML An error occurred while:\n";
    echo "error message：$errorMessage\n";
    echo "Error code：$errorCode\n";
    echo "Error row count：$lineNumber\n";

    // Error logging，或者引导user查看帮助页面
    // Example：Log errors to log file
    error_log("XML Analysis错误：$errorMessage In the $lineNumber OK", 3, "/var/log/xml_errors.log");

    // Or show a help link
    echo "Please refer to the help document：https://m66.net/xml/help\n";
} else {
    echo "? XML Analysis成功！\n";
}

// 释放Parser资源
xml_parser_free($parser);
?>

analyze

  1. xml_parser_create()
    Creates an XML parser resource that is later used to parse XML strings.

  2. xml_parse()
    Parses the provided XML string. If parsing fails, false is returned.

  3. xml_get_error_code() / xml_error_string()
    Get the error code and convert it into readable error information.

  4. xml_get_current_line_number()
    Get the line number when an error occurs, which facilitates quick positioning of problems.

  5. xml_parser_free()
    Release resources after parsing is completed to avoid memory leaks.

Application scenarios

This method is very suitable for the following scenarios:

  • Format verification when users upload XML files;

  • Fault-tolerant processing when third-party interfaces return XML data;

  • Pre-checking logic in automated data import system;

  • Instant check of XML format in online editor.

Tips

  • Using libxml extensions with DOM or SimpleXML provides more advanced XML operation methods, but the underlying original parsers such as xml_parse are more efficient when handling large-scale data streams.

  • Never trust external XML data directly. In addition to format errors, it may also be injected into malicious entities (XXE attacks). Remember to turn off the entity parsing function.

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