我有这个xml，当我尝试获取节点时：InternetGatewayDevice-＆gt; WANDevice-＆gt; i2与getElementsByTagName失败。它仅适用于xpath。这是代码：
XML：
<?xml version="1.0" encoding="UTF-8"?>
<InternetGatewayDevice>
<LANDevice>
<i1>
</i1>
</LANDevice>
<Time>
<X_ZyXEL_DefaultRouteProfileName PARAMETER="configured" TYPE="string" LENGTH="256"></X_ZyXEL_DefaultRouteProfileName>
<LocalTimeZoneName PARAMETER="configured" TYPE="string" LENGTH="64">CET-1CEST-2,M3.5.0/1,M10.5.0/1</LocalTimeZoneName>
<NTPServer5 PARAMETER="configured" TYPE="string" LENGTH="64"></NTPServer5>
<NTPServer4 PARAMETER="configured" TYPE="string" LENGTH="64"></NTPServer4>
<NTPServer3 PARAMETER="configured" TYPE="string" LENGTH="64"></NTPServer3>
<NTPServer2 PARAMETER="configured" TYPE="string" LENGTH="64"></NTPServer2>
<NTPServer1 PARAMETER="configured" TYPE="string" LENGTH="64">europe.pool.ntp.org</NTPServer1>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</Time>
<WANDevice>
<i1>
<WANEthernetInterfaceConfig>
<DuplexMode PARAMETER="configured" TYPE="string" LENGTH="32">Auto</DuplexMode>
<MaxBitRate PARAMETER="configured" TYPE="string" LENGTH="32">Auto</MaxBitRate>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</WANEthernetInterfaceConfig>
<WANConnectionDevice>
<i1>
<X_ZyXEL_WANService PARAMETER="configured" TYPE="string" LENGTH="63"></X_ZyXEL_WANService>
<X_ZyXEL_EgressQueue PARAMETER="configured" TYPE="uint8" MAX="255" MIN="0">0</X_ZyXEL_EgressQueue>
<X_ZyXEL_L2VlanMuxMode PARAMETER="configured" TYPE="boolean">1</X_ZyXEL_L2VlanMuxMode>
<WANIPConnection>
<i1>
<X_ZyXEL_IPv6DefaultGateway PARAMETER="configured" TYPE="string" LENGTH="46">fe80::1</X_ZyXEL_IPv6DefaultGateway>
<RouteProtocolRx PARAMETER="configured" TYPE="string" LENGTH="10">Off</RouteProtocolRx>
<ConnectionTrigger PARAMETER="configured" TYPE="string" LENGTH="10">AlwaysOn</ConnectionTrigger>
<X_ZyXEL_Multicast PARAMETER="configured" TYPE="string" LENGTH="8">IGMPv3</X_ZyXEL_Multicast>
<DNSServers PARAMETER="configured" TYPE="string" LENGTH="64"></DNSServers>
<DefaultGateway PARAMETER="configured" TYPE="string" LENGTH="16"></DefaultGateway>
<SubnetMask PARAMETER="configured" TYPE="string" LENGTH="16"></SubnetMask>
<ExternalIPAddress PARAMETER="configured" TYPE="string" LENGTH="16"></ExternalIPAddress>
<AddressingType PARAMETER="configured" TYPE="string" LENGTH="8">DHCP</AddressingType>
<Name PARAMETER="configured" TYPE="string" LENGTH="256">EtherWAN1</Name>
<ConnectionType PARAMETER="configured" TYPE="string" LENGTH="13">IP_Routed</ConnectionType>
<X_ZyXEL_DualStack PARAMETER="configured" TYPE="uint8" MAX="2" MIN="0">1</X_ZyXEL_DualStack>
<X_ZyXEL_PassThrough PARAMETER="configured" TYPE="boolean">0</X_ZyXEL_PassThrough>
<X_ZyXEL_Routing PARAMETER="configured" TYPE="uint8" MAX="2" MIN="0">1</X_ZyXEL_Routing>
<X_ZyXEL_VlanMux8021p PARAMETER="configured" TYPE="uint8" MAX="7" MIN="0">0</X_ZyXEL_VlanMux8021p>
<MACAddressOverride PARAMETER="configured" TYPE="boolean">0</MACAddressOverride>
<MACAddress PARAMETER="configured" TYPE="mac">00:00:00:00:00:00</MACAddress>
<X_ZyXEL_AutoBridge PARAMETER="configured" TYPE="boolean">0</X_ZyXEL_AutoBridge>
<DNSOverrideAllowed PARAMETER="configured" TYPE="boolean">0</DNSOverrideAllowed>
<DNSEnabled PARAMETER="configured" TYPE="boolean">1</DNSEnabled>
<NATEnabled PARAMETER="configured" TYPE="boolean">1</NATEnabled>
<X_ZyXEL_L2Bridging_AvailableInterfaceKey PARAMETER="configured" TYPE="uint8" MAX="255" MIN="0">17</X_ZyXEL_L2Bridging_AvailableInterfaceKey>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
<X_ZyXEL_VLanMuxId PARAMETER="configured" TYPE="uint16" MAX="4094" MIN="0">3900</X_ZyXEL_VLanMuxId>
<MaxMTUSize PARAMETER="configured" TYPE="uint16" MAX="1540" MIN="1">1500</MaxMTUSize>
<ShapingRate PARAMETER="configured" TYPE="sint31" MAX="2147483647" MIN="-1">-1</ShapingRate>
<X_ZyXEL_IPv6DNS>
<i1>
<ServerIP PARAMETER="configured" TYPE="string" LENGTH="46">::1</ServerIP>
<ServerType PARAMETER="configured" TYPE="string" LENGTH="32">FromISP</ServerType>
</i1>
</X_ZyXEL_IPv6DNS>
<X_ZyXEL_NAT>
<DefaultServerIP PARAMETER="configured" TYPE="string" LENGTH="16"></DefaultServerIP>
<DefaultServerIPEnabled PARAMETER="configured" TYPE="boolean">0</DefaultServerIPEnabled>
<Loopback PARAMETER="configured" TYPE="boolean">0</Loopback>
<LookupRule>
<i1>
<GlobalEnd PARAMETER="configured" TYPE="string" LENGTH="16">0.0.0.0</GlobalEnd>
<GlobalStart PARAMETER="configured" TYPE="string" LENGTH="16">0.0.0.0</GlobalStart>
<LocalEnd PARAMETER="configured" TYPE="string" LENGTH="16">255.255.255.255</LocalEnd>
<LocalStart PARAMETER="configured" TYPE="string" LENGTH="16">0.0.0.0</LocalStart>
<DeviceWANIP PARAMETER="configured" TYPE="boolean">1</DeviceWANIP>
<NATRuleEnabled PARAMETER="configured" TYPE="boolean">1</NATRuleEnabled>
<Type PARAMETER="configured" TYPE="uint8" MAX="3" MIN="0">1</Type>
</i1>
</LookupRule>
</X_ZyXEL_NAT>
<X_ZyXEL_IPv6GlobalAddress>
<i1>
<Address PARAMETER="configured" TYPE="string" LENGTH="46">::</Address>
<AddressingType PARAMETER="configured" TYPE="string" LENGTH="10">DHCPv6</AddressingType>
<PrefixLength PARAMETER="configured" TYPE="uint8" MAX="64" MIN="16">64</PrefixLength>
</i1>
</X_ZyXEL_IPv6GlobalAddress>
<X_ZyXEL_DNS>
<i1>
<ServerIP PARAMETER="configured" TYPE="string" LENGTH="16">0.0.0.0</ServerIP>
<ServerType PARAMETER="configured" TYPE="string" LENGTH="32">FromISP</ServerType>
</i1>
</X_ZyXEL_DNS>
<X_ZyXEL_DHCPv6Client>
<SentDHCPOption>
<i1>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">25</Tag>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</i1>
<i2>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">3</Tag>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</i2>
<i3>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">23</Tag>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</i3>
</SentDHCPOption>
</X_ZyXEL_DHCPv6Client>
<DHCPClient>
<SentDHCPOption>
<i1>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">60</Tag>
<Enable PARAMETER="configured" TYPE="boolean">0</Enable>
</i1>
</SentDHCPOption>
</DHCPClient>
</i1>
</WANIPConnection>
</i1>
</WANConnectionDevice>
</i1>
<i2>
<WANDSLInterfaceConfig>
<LinkEncapsulationRequested PARAMETER="configured" TYPE="string" LENGTH="64">G.992.3_Annex_K_ATM</LinkEncapsulationRequested>
<Status PARAMETER="configured" TYPE="string" LENGTH="64">Up</Status>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</WANDSLInterfaceConfig>
<WANConnectionDevice>
<i1>
<X_ZyXEL_WANService PARAMETER="configured" TYPE="string" LENGTH="63"></X_ZyXEL_WANService>
<X_ZyXEL_EgressQueue PARAMETER="configured" TYPE="uint8" MAX="255" MIN="0">0</X_ZyXEL_EgressQueue>
<X_ZyXEL_L2VlanMuxMode PARAMETER="configured" TYPE="boolean">0</X_ZyXEL_L2VlanMuxMode>
<WANPPPConnection>
<i1>
<X_ZyXEL_PPPAuthenticationProtocol PARAMETER="configured" TYPE="string" LENGTH="32">Auto</X_ZyXEL_PPPAuthenticationProtocol>
<RouteProtocolRx PARAMETER="configured" TYPE="string" LENGTH="10">Off</RouteProtocolRx>
<ConnectionTrigger PARAMETER="configured" TYPE="string" LENGTH="10">AlwaysOn</ConnectionTrigger>
<PPPoEServiceName PARAMETER="configured" TYPE="string" LENGTH="256"></PPPoEServiceName>
<PPPoEACName PARAMETER="configured" TYPE="string" LENGTH="256"></PPPoEACName>
<X_ZyXEL_Multicast PARAMETER="configured" TYPE="string" LENGTH="8">IGMPv3</X_ZyXEL_Multicast>
<DNSServers PARAMETER="configured" TYPE="string" LENGTH="64"></DNSServers>
<Password PARAMETER="configured" TYPE="string" LENGTH="64">a</Password>
<Username PARAMETER="configured" TYPE="string" LENGTH="64">ads</Username>
<Name PARAMETER="configured" TYPE="string" LENGTH="256">AdslWAN1</Name>
<ConnectionType PARAMETER="configured" TYPE="string" LENGTH="16">IP_Routed</ConnectionType>
<X_ZyXEL_StaticIP PARAMETER="configured" TYPE="string" LENGTH="16">1xx.20.7.5</X_ZyXEL_StaticIP>
<X_ZyXEL_DualStack PARAMETER="configured" TYPE="uint8" MAX="2" MIN="0">0</X_ZyXEL_DualStack>
<X_ZyXEL_Routing PARAMETER="configured" TYPE="uint8" MAX="2" MIN="0">1</X_ZyXEL_Routing>
<X_ZyXEL_VlanMux8021p PARAMETER="configured" TYPE="uint8" MAX="7" MIN="0">0</X_ZyXEL_VlanMux8021p>
<X_ZyXEL_PassThrough PARAMETER="configured" TYPE="boolean">1</X_ZyXEL_PassThrough>
<MACAddressOverride PARAMETER="configured" TYPE="boolean">0</MACAddressOverride>
<MACAddress PARAMETER="configured" TYPE="mac">xx</MACAddress>
<X_ZyXEL_AutoBridge PARAMETER="configured" TYPE="boolean">0</X_ZyXEL_AutoBridge>
<DNSOverrideAllowed PARAMETER="configured" TYPE="boolean">0</DNSOverrideAllowed>
<DNSEnabled PARAMETER="configured" TYPE="boolean">1</DNSEnabled>
<NATEnabled PARAMETER="configured" TYPE="boolean">0</NATEnabled>
<X_ZyXEL_L2Bridging_AvailableInterfaceKey PARAMETER="configured" TYPE="uint8" MAX="255" MIN="0">0</X_ZyXEL_L2Bridging_AvailableInterfaceKey>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
<X_ZyXEL_VLanMuxId PARAMETER="configured" TYPE="uint16" MAX="4094" MIN="0">0</X_ZyXEL_VLanMuxId>
<ShapingRate PARAMETER="configured" TYPE="sint31" MAX="2147483647" MIN="-1">-1</ShapingRate>
<IdleDisconnectTime PARAMETER="configured" TYPE="uint32" MAX="4294967295" MIN="0">0</IdleDisconnectTime>
<AutoDisconnectTime PARAMETER="configured" TYPE="uint32" MAX="4294967295" MIN="0">0</AutoDisconnectTime>
<X_ZyXEL_DNS>
<i1>
<ServerIP PARAMETER="configured" TYPE="string" LENGTH="16">xx</ServerIP>
<ServerType PARAMETER="configured" TYPE="string" LENGTH="32">UserDefined</ServerType>
</i1>
<i2>
<ServerIP PARAMETER="configured" TYPE="string" LENGTH="16">xx</ServerIP>
<ServerType PARAMETER="configured" TYPE="string" LENGTH="32">UserDefined</ServerType>
</i2>
</X_ZyXEL_DNS>
<X_ZyXEL_IPv6GlobalAddress>
<i1>
<Address PARAMETER="configured" TYPE="string" LENGTH="46">::</Address>
<AddressingType PARAMETER="configured" TYPE="string" LENGTH="10">DHCPv6</AddressingType>
<PrefixLength PARAMETER="configured" TYPE="uint8" MAX="64" MIN="16">64</PrefixLength>
</i1>
</X_ZyXEL_IPv6GlobalAddress>
<X_ZyXEL_IPv6DNS>
<i1>
<ServerIP PARAMETER="configured" TYPE="string" LENGTH="46">::</ServerIP>
<ServerType PARAMETER="configured" TYPE="string" LENGTH="32">FromISP</ServerType>
</i1>
</X_ZyXEL_IPv6DNS>
<X_ZyXEL_DHCPv6Client>
<SentDHCPOption>
<i1>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">25</Tag>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</i1>
<i2>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">3</Tag>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</i2>
<i3>
<Value PARAMETER="configured" TYPE="string" LENGTH="340"></Value>
<Tag PARAMETER="configured" TYPE="uint8" MAX="254" MIN="1">23</Tag>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
</i3>
</SentDHCPOption>
</X_ZyXEL_DHCPv6Client>
</i1>
</WANPPPConnection>
<WANDSLLinkConfig>
<X_ZyXEL_IfName PARAMETER="configured" TYPE="string" LENGTH="16">nas1</X_ZyXEL_IfName>
<ATMQoS PARAMETER="configured" TYPE="string" LENGTH="128">UBR</ATMQoS>
<ATMEncapsulation PARAMETER="configured" TYPE="string" LENGTH="64">LLC</ATMEncapsulation>
<DestinationAddress PARAMETER="configured" TYPE="string" LENGTH="256">PVC:8/35</DestinationAddress>
<LinkType PARAMETER="configured" TYPE="string" LENGTH="32">EoA</LinkType>
<X_ZyXEL_ATMEnbQos PARAMETER="configured" TYPE="boolean">0</X_ZyXEL_ATMEnbQos>
<Enable PARAMETER="configured" TYPE="boolean">1</Enable>
<X_ZyXEL_ATMSendBuffer PARAMETER="configured" TYPE="uint16" MAX="26144" MIN="0">0</X_ZyXEL_ATMSendBuffer>
<ATMSustainableCellRate PARAMETER="configured" TYPE="uint32" MAX="4294967295" MIN="0">0</ATMSustainableCellRate>
<ATMMaximumBurstSize PARAMETER="configured" TYPE="uint32" MAX="4294967295" MIN="0">0</ATMMaximumBurstSize>
<ATMPeakCellRate PARAMETER="configured" TYPE="uint32" MAX="4294967295" MIN="0">0</ATMPeakCellRate>
</WANDSLLinkConfig>
</i1>
</WANConnectionDevice>
<WANDSLDiagnostics>
<LoopDiagnosticsState PARAMETER="configured" EXTATTR="0x0002" TYPE="string" LENGTH="32">Complete</LoopDiagnosticsState>
</WANDSLDiagnostics>
</i2>
</WANDevice>
</InternetGatewayDevice>
php：
$xml = new DOMDocument('1.0', 'utf-8');
$xml->formatOutput = true;
$xml->preserveWhiteSpace = false;
$xml->load('file.xml');
//With getElementsByTagName
echo "getElementsByTagName:<br/>";
$node_of_xml = $xml->getElementsByTagName('InternetGatewayDevice')->item(0)->getElementsByTagName('WANDevice')->item(0)->getElementsByTagName('i2')->item(0);
foreach($node_of_xml->childNodes as $child) {
echo $child->nodeName ."<br/>";
}
//With xpath
echo "<br/>Xpath:<br/>";
$xpath = new DOMXPath($xml);
$results = $xpath->query('/InternetGatewayDevice/WANDevice/i2');
$node_of_xml = $results->item(0);
foreach($node_of_xml->childNodes as $child) {
echo $child->nodeName ."<br/>";
}
输出（getElementsByTagName错误，Xpath正确）：
getElementsByTagName:
Value
Tag
Enable
Xpath:
WANDSLInterfaceConfig
WANConnectionDevice
WANDSLDiagnostics
PHP Version 5.3.20 DOM / XML已启用 DOM / XML API Version 20031129 libxml版本2.7.8
答案 0 :(得分：0)
getElementsByTagName不仅限于直接儿童。 i2中的第一个WANDevice节点是/InternetGatewayDevice/WANDevice/i1/WANConnectionDevice/i1/WANIPConnection/i1/X_ZyXEL_DHCPv6Client/SentDHCPOption/i2
您自己提供了解决方案：XPath。