RFC: Custom callback to dump results in php -a

[TysonAndre]

RFC: https://wiki.php.net/rfc/readline_interactive_shell_result_function

1. This adds readline_interactive_shell_result_function()
   that can be used to configure a custom callback to dump results of standalone expressions.
   (For interactive shells)
2. This also adds a default dumper for expressions, which behaves like the following snippet. (see test cases)
3. The original behavior of never dumping expression results can be restored by setting cli.enable_interactive_shell_result_function=0

readline_interactive_shell_result_function(
    function(string $code, $result) {
        if (!isset($result)) {
            return;
        }
        if (is_scalar($result)) {
            echo "=> " . var_export($result, true) . "\n";
        } else {
            echo "=> "; var_dump($result);
        }});

See ext/readline/tests/readline_interactive_result.phpt for an example of how a
customized callback could be set.

Those hooks can use projects such as php-parser or php-ast to customize
the logic of whether the value of assignments or print() expressions
should not be printed.
Example usage:

readline_interactive_shell_result_function(
    function (string $code, $result) {
        echo "Saw " . trim($code) . "\n";
        echo json_encode($result);
    });

The system ini setting cli.enable_interactive_shell_result_function
can be used to disable this functionality to debug applications that load
buggy handlers. It is enabled by default.

Currently, this only attempts to support single expressions terminated by ;,
if the ini setting is enabled, a handler is configured, and parsing the code doesn't throw a ParseError/CompileError.
See ext/readline/tests/libedit_interactive_result.phpt for an example session.

Related to https://externals.io/message/111073

[nikic]

Closing this as the RFC has been declined: https://wiki.php.net/rfc/readline_interactive_shell_result_function#vote