Working with Environment Variables

GrepOptions carries an ignoreCase flag and search() honors it, but fromArgv() still hardcodes it to false. Nobody running phpgrep from a terminal can turn it on. Let’s fix that with an environment variable rather than a third argument.

Why not simply $argv[3]? Because ignoring case is closer to a standing preference than a per-search decision. It is something you may want on for every search in a shell session, without retyping a flag each time. An environment variable is set once and inherited by every command you run afterward, until you close the terminal or unset it. That is exactly the tool for a preference.

Reading it with getenv()

<?php
// src/GrepOptions.php
declare(strict_types=1);

final class GrepOptions
{
    public function __construct(
        public readonly string $query,
        public readonly string $filename,
        public readonly bool $ignoreCase,
    ) {
    }

    public static function fromArgv(array $argv): self
    {
        return new self(
            query: $argv[1],
            filename: $argv[2],
            ignoreCase: getenv('PHPGREP_IGNORE_CASE') !== false,
        );
    }
}

getenv('PHPGREP_IGNORE_CASE') returns the variable’s value as a string if it is set, and the boolean false if it is not set at all. That is why the check is !== false rather than an attempt to interpret the value. It means PHPGREP_IGNORE_CASE=1 turns the flag on, but so does PHPGREP_IGNORE_CASE= with nothing after the =: an empty string is still a value, and setting the variable at all counts as “on”. If that looseness bothers you, you are right to notice it. Tightening it (say, requiring the value to be exactly "1") is a good improvement to make on your own once the chapter is done.

Trying it

$ php phpgrep.php APPLE fruits.txt

No output at all: APPLE, compared case-sensitively, appears in neither the Apple line nor the apple line. Now flip the flag on:

$ PHPGREP_IGNORE_CASE=1 php phpgrep.php APPLE fruits.txt
Apple pie recipe
apple sauce for the win

Writing PHPGREP_IGNORE_CASE=1 just before the command, on the same line, sets it for that one invocation only. It is a common shell idiom for a setting that should not outlive the command it is attached to. Export it instead, and it sticks around for the rest of the session:

$ export PHPGREP_IGNORE_CASE=1
$ php phpgrep.php APPLE fruits.txt
Apple pie recipe
apple sauce for the win

getenv() versus $_ENV

PHP also exposes the environment through the $_ENV superglobal, and you should know why this chapter did not reach for it. $_ENV is only filled according to the variables_order setting in php.ini. On plenty of default installations, especially ones tuned for serving web pages, the E is missing from that setting, and $_ENV stays empty whatever the process environment holds. getenv() has no such dependency: it asks the operating system directly, every time, and behaves the same in CLI scripts, web requests and every hosting setup you are likely to meet. For a tool meant to run reliably wherever it is installed, that consistency is worth the slightly less fashionable syntax.