File: vendor/squizlabs/php_codesniffer/src/Standards/Generic/Docs/Strings/UnnecessaryHeredocStandard.xml

<documentation title="Unnecessary Heredoc">
    <standard>
    <![CDATA[
    If no interpolation or expressions are used in the body of a heredoc, nowdoc syntax should be used instead.
    ]]>
    </standard>
    <code_comparison>
        <code title="Valid: Using nowdoc syntax for a text string without any interpolation or expressions.">
        <![CDATA[
$nowdoc = <em><<<'EOD'</em>
some text
EOD;
        ]]>
        </code>
        <code title="Invalid: Using heredoc syntax for a text string without any interpolation or expressions.">
        <![CDATA[
$heredoc = <em><<<EOD</em>
some text
EOD;
        ]]>
        </code>
    </code_comparison>
    <code_comparison>
        <code title="Valid: Using heredoc syntax for a text string containing interpolation or expressions.">
        <![CDATA[
$heredoc = <em><<<"EOD"</em>
some $text
EOD;
        ]]>
        </code>
        <code title="Invalid: Using heredoc syntax for a text string without any interpolation or expressions.">
        <![CDATA[
$heredoc = <em><<<"EOD"</em>
some text
EOD;
        ]]>
        </code>
    </code_comparison>
</documentation>