composer require "ralfmaxxx/phpmd_variable_lifetime"
And append this rule to phpmd.xml using definition file rulesets/design.xml:
<rule ref="{path}/rulesets/design.xml/LocalVariableLifetime" />
You can additionally set allowed lines interval parameter:
<rule ref="{path}/rulesets/design.xml/LocalVariableLifetime">
<properties>
<property name="allowedLinesInterval" value="5"/>
</properties>
</rule>