php 60 lines · 9 steps

Writing a .env file loader in PHP

A self-contained class that parses a .env file line by line and injects the values into the environment.

Explained by highlit

Intermediate parsing environment-variables configuration string-handling

1<?php
2 
3namespace App\Config;
4 
5final class DotenvLoader
6{
7    public static function load(string $path): void
8    {
9        if (!is_readable($path)) {
10            throw new \RuntimeException("Env file not found or unreadable: {$path}");
11        }
12 
13        $lines = file($path, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
14 
15        foreach ($lines as $line) {
16            $line = trim($line);
17 
18            if ($line === '' || str_starts_with($line, '#')) {
19                continue;
20            }
21 
22            if (!str_contains($line, '=')) {
23                continue;
24            }
25 
26            [$name, $value] = explode('=', $line, 2);
27            $name = trim($name);
28            $value = self::normalize(trim($value));
29 
30            if (getenv($name) !== false || array_key_exists($name, $_ENV)) {
31                continue;
32            }
33 
34            putenv("{$name}={$value}");
35            $_ENV[$name] = $value;
36            $_SERVER[$name] = $value;
37        }
38    }
39 
40    private static function normalize(string $value): string
41    {
42        if ($value === '') {
43            return $value;
44        }
45 
46        $quote = $value[0];
47 
48        if (($quote === '"' || $quote === "'") && str_ends_with($value, $quote)) {
49            $value = substr($value, 1, -1);
50 
51            if ($quote === '"') {
52                $value = str_replace(['\\n', '\\"'], ["\n", '"'], $value);
53            }
54 
55            return $value;
56        }
57 
58        return preg_replace('/\s+#.*$/', '', $value) ?? $value;
59    }
60}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Refusing to overwrite pre-existing environment variables lets real system config take precedence over the file.
2Splitting on the first delimiter with a limit keeps values containing that delimiter intact.
3Quoted values need their own normalization rules distinct from bare, comment-trailed values.

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