File: vendor/squizlabs/php_codesniffer/src/Standards/Generic/Docs/Formatting/SpaceAfterNotStandard.xml

<documentation title="Space After NOT operator">
    <standard>
    <![CDATA[
    Exactly one space is allowed after the NOT operator.
    ]]>
    </standard>
    <code_comparison>
        <code title="Valid: A NOT operator followed by one space.">
        <![CDATA[
if (!<em> </em>$someVar || !<em> </em>$x instanceOf stdClass) {};
        ]]>
        </code>
        <code title="Invalid: A NOT operator not followed by whitespace.">
        <![CDATA[
if (!<em></em>$someVar || !<em></em>$x instanceOf stdClass) {};
        ]]>
        </code>
        <code title="Invalid: A NOT operator followed by a new line or more than one space.">
        <![CDATA[
if (!<em>     </em>$someVar || !<em>
    </em>$x instanceOf stdClass) {};
        ]]>
        </code>
    </code_comparison>
</documentation>