Read input and produce clear output.

LESSON OBJECTIVE

What you will be able to do

Read input safely, choose the correct output channel, validate values, and return meaningful exit statuses.

stdout, stderr, and stdin

echo writes normal output. STDERR is for diagnostics. fgets(STDIN) reads a line and may return false, so trim only after checking it.

$line = fgets(STDIN);
if ($line === false) {
    fwrite(STDERR, "Input unavailable\n");
    exit(1);
}
$name = trim($line);

Validate after reading

A string from the terminal remains a string. Validate ranges and formats before converting or constructing domain objects.

Choose useful exit codes

Return 0 for success and a non-zero status for invalid usage or failure so scripts can react correctly.