File: vendor/squizlabs/php_codesniffer/src/Standards/Generic/Docs/WhiteSpace/HereNowdocIdentifierSpacingStandard.xml

<documentation title="Heredoc Nowdoc Identifier Spacing">
    <standard>
    <![CDATA[
    There should be no space between the <<< and the heredoc/nowdoc identifier string.
    ]]>
    </standard>
    <code_comparison>
        <code title="Valid: No space between the &lt;&lt;&lt; and the identifier string.">
        <![CDATA[
$heredoc = <em><<<EOD</em>
some text
EOD;
        ]]>
        </code>
        <code title="Invalid: Whitespace between the &lt;&lt;&lt; and the identifier string.">
        <![CDATA[
$heredoc = <em><<<   END</em>
some text
END;
        ]]>
        </code>
    </code_comparison>
</documentation>