<?php

namespace Psy;

/**
 * Command to return the eval-able code to startup PsySH.
 *
 * ~~~php
 * eval(\Psy\sh());
 * ~~~
 *
 * @return string
 */
function sh()
{
    return "extract(\Psy\Shell::debug(get_defined_vars()));";
}

<?php

namespace Psy;

/**
 * Command to return the eval-able code to startup PsySH.
 *
 *     eval(\Psy\sh());
 *
 * @return string
 */
function sh()
{
    return "extract(\Psy\Shell::debug(get_defined_vars()));";
}

Use indented code block instead of fenced.
Use indented code block instead of fenced.

Indented is a bit better for human consumption, and these docblocks are more for humans than robots.