PHP.如何使用curl在POST正文中仅发送xml文本 - PHP. how to send ONLY xml text in POST body use curl?

PHP. how to send ONLY xml text in POST body use curl?

我需要在POST正文中发送xml（它必须只包含xml文本）。我使用这样的代码，但我不知道如何转义像'<?xml'、'?>'这样的字符。

<?php
$url = 'http://' . $_SERVER[ 'SERVER_NAME' ] . '/api/setExchangeRate/';
$xmlcontent = "<?xml version="1.0" encoding="WINDOWS-1251"?>" .
    '<Data>
    <Off UID="0001">
    <SetupDateTime>DD MM YYYY HH:MM</SetupDateTime>
    <Currency CODE="840">
    <Buy>67.50</Buy>
    <Sell>67.50</Sell>
    </Currency>
    <Currency CODE="978">
    <Buy>75.40</Buy>
    <Sell>77.10</Sell>
    </Currency>
    </Off>
    </Data>';
$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_URL, $url );
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $xmlcontent);
$content=curl_exec($ch);
print_r( $content );

服务器端的print_r( $_POST )返回错误代码：

(
    [<?xml_version] => "1.0" encoding="WINDOWS-1251"?><Data>
<Off UID="0001">
<SetupDateTime>DD MM YYYY HH:MM</SetupDateTime>
<Currency CODE="840">
<Buy>67.50</Buy>
<Sell>67.50</Sell>
</Currency>
<Currency CODE="978">
<Buy>75.40</Buy>
<Sell>77.10</Sell>
</Currency>
</Off>
</Data>
)

在不转义的情况下，不能在引号中使用相同类型的引号：

错误：

"<?xml version="1.0" encoding="WINDOWS-1251"?>"

应为：

"<?xml version='"1.0'" encoding='"WINDOWS-1251'"?>"

或者只需将外部双引号替换为单引号：

'<?xml version="1.0" encoding="WINDOWS-1251"?>'