What is CodeIgniter 4 CLI application development?
Why Interviewers Ask This
This is a differentiating question used for senior and lead roles. Interviewers want to see if you can explain not just what happens, but why — and what the trade-offs are in different approaches.
Answer
CI4 is well-suited for building CLI applications beyond just Spark commands. Detect CLI context: is_cli(). CI4 CLI apps can: process queues, run scheduled jobs, import/export data, send batch emails, and perform database maintenance. The CLI class provides rich output: CLI::write("text", "color") (colors: green, red, yellow, blue), CLI::table($headers, $rows), CLI::progressBar($total), CLI::printProgress($current, $total). Capture input: CLI::input("Press Enter to continue"), CLI::confirm("Are you sure?"), CLI::promptByKey("Choose", $options). Parse CLI arguments from $_SERVER["argv"]. Long-running scripts: increase ini_set("max_execution_time", 0) and memory_limit. For daemon processes (run forever), use a while loop with a sleep: while (true) { $this->process(); sleep(5); }. Use Supervisor to manage long-running CI4 CLI processes in production.
Common Mistake
A common mistake is memorizing definitions without understanding implications. When asked this question, go one level deeper — explain what happens when this concept is misused or ignored.