array2xml
/**
     *
     * 将简单数组转化为简单的xml
     * @param string $data  要进行转化的数组
     * @param string $tag   要使用的标签
     * @example
     * $arr = array(
        'rtxAccount'=>'aaron','ipAddr'=>'192.168.0.12',
        'conferenceList'=>array('conference'=>
                            array(
                                array('conferenceId'=>1212,'conferenceTitle'=>'quanshi 444','smeAccount'=>'http://www.jb51.net'),
                                array('conferenceId'=>454,'conferenceTitle'=>'quanshi meetting','smeAccount'=>'http://www.jb51.net'),
                                array('conferenceId'=>6767,'conferenceTitle'=>'quanshi meetting','smeAccount'=>'http://www.jb51.net'),
                                array('conferenceId'=>232323,'conferenceTitle'=>'quanshi uuu','smeAccount'=>'http://www.jb51.net'),
                                array('conferenceId'=>8989,'conferenceTitle'=>'quanshi meetting','smeAccount'=>'http://www.jb51.net'),
                                array('conferenceId'=>1234343212,'conferenceTitle'=>'quanshi meetting','smeAccount'=>'http://www.jb51.net')
                                )
                            )
        );
        转化为：
        <rtxAccount>aaron</rtxAccount>
        <ipAddr>192.168.0.12</ipAddr>
        <conferenceList>
            <conference>
                <conferenceId>1212</conferenceId>
                <conferenceTitle>quanshi 444</conferenceTitle>
                <smeAccount>http://www.jb51.net</smeAccount>
            </conference>
            <conference>
                <conferenceId>454</conferenceId>
                <conferenceTitle>quanshi meetting</conferenceTitle>
                <smeAccount>http://www.jb51.net</smeAccount>
            </conference>
            <conference>
                <conferenceId>6767</conferenceId>
                <conferenceTitle>quanshi meetting</conferenceTitle>
                <smeAccount>http://www.jb51.net</smeAccount>
            </conference>
            <conference>
                <conferenceId>232323</conferenceId>
                <conferenceTitle>quanshi uuu</conferenceTitle>
                <smeAccount>http://www.jb51.net</smeAccount>
            </conference>
            <conference>
                <conferenceId>8989</conferenceId>
                <conferenceTitle>quanshi meetting</conferenceTitle>
                <smeAccount>http://www.jb51.net</smeAccount>
            </conference>
            <conference>
                <conferenceId>1234343212</conferenceId>
                <conferenceTitle>quanshi meetting</conferenceTitle>
                <smeAccount>http://www.jb51.net</smeAccount>
            </conference>
        </conferenceList>
     */
    function array2xml($data,$tag = '')
    {
        $xml = '';

foreach($data as $key => $value)
        {
            if(is_numeric($key))
            {
                if(is_array($value))
                {
                    $xml .= "<$tag>";
                    $xml .= array2xml($value);
                    $xml .="</$tag>";
                }
                else
                {
                    $xml .= "<$tag>$value</$tag>";
                }   
            }
            else
            {
                if(is_array($value))
                {
                    $keys = array_keys($value);
                    if(is_numeric($keys[0]))
                    {
                        $xml .=array2xml($value,$key);
                    }
                    else
                    {
                        $xml .= "<$key>";
                        $xml .=array2xml($value);
                        $xml .= "</$key>";
                    }

}
                else
                {
                    $xml .= "<$key>$value</$key>";
                }
            }
        }
        return $xml;
    }            
}

xml2array

/**
  *
  * 将简单的xml转化成关联数组
  * @param string $xmlString  xml字符串
  * @example
  * <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<RTXConferenceReqDTO>
 <conferenceTitle>IT交流会</conferenceTitle>
 <startTime>2011-12-19 12:00:00</startTime>
 <rtxAccount>andy1111111</rtxAccount>
 <ipAddr>192.168.1.56</ipAddr>
 <duration>120</duration>
 <conferenceType>1</conferenceType>
 <invitees>
  <invitee>
   <rtxAccount>被邀请人1的RTX账号</rtxAccount>
   <tel>被邀请人1电话号码</tel>
  </invitee>
  <invitee>
   <rtxAccount>被邀请人2的RTX账号</rtxAccount>
   <tel>被邀请人2电话号码</tel>
  </invitee>
 </invitees>
</RTXConferenceReqDTO>
转化之后的关联数组：
Array
(
    [conferenceTitle] => IT交流会
    [startTime] => 2011-12-19 12:00:00
    [rtxAccount] => andy1111111
    [ipAddr] => 192.168.1.56
    [duration] => 120
    [conferenceType] => 1
    [invitees] => Array
        (
            [invitee] => Array
                (
                    [0] => Array
                        (
                            [rtxAccount] => 被邀请人1的RTX账号
                            [tel] => 被邀请人1电话号码
                        )
                    [1] => Array
                        (
                            [rtxAccount] => 被邀请人2的RTX账号
                            [tel] => 被邀请人2电话号码
                        )
                )
        )
)
  */
 function xml2array($xmlString = '')
 {
  $targetArray = array();
  $xmlObject = simplexml_load_string($xmlString);
  $mixArray = (array)$xmlObject;
  foreach($mixArray as $key => $value)
  {
   if(is_string($value))
   {
    $targetArray[$key] = $value;
   }
   if(is_object($value))
   {
    $targetArray[$key] = xml2array($value->asXML());
   }
   if(is_array($value))
   {
    foreach($value as $zkey => $zvalue)
    {
     if(is_numeric($zkey))
     {
      $targetArray[$key][] = xml2array($zvalue->asXML());
     }
     if(is_string($zkey))
     {
      $targetArray[$key][$zkey] = xml2array($zvalue->asXML());
     }
    }
   }
  }
  return $targetArray;

}