Whenever you have variables in your heredoc, you will want to use double quotes in the example dws suggests. Otherwise the here doc will be single-quotish and the variables will not interpolate:

    $sql = <<"    EOSQL";
    ...
    EOSQL
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This technique breaks of course if you change the indenting on the heredoc itself without changing the indent on the '<<' line. So you will need to decide if the readability is sufficient advantage to make up for the maintenance issue.