Can constants replace .env configuration files? Practical comparison

In PHP project development, there are usually many options for managing configuration files. .env files are one of the widely used methods of current mainstream frameworks (such as Laravel). They support flexible configuration and dynamic reading of environment variables. However, some developers have suggested: Can PHP constants ( define ) be used instead of .env files? This article will use the get_defined_constants function to analyze the advantages and disadvantages of the two in terms of performance, security, flexibility, etc.

1. What is .env file and constant configuration

.env files are usually used to store environment-related configurations, such as database connection information, API keys, etc.:

 APP_ENV=production
DB_HOST=127.0.0.1
DB_PORT=3306

The way to define constants in PHP is:

 define('APP_ENV', 'production');
define('DB_HOST', '127.0.0.1');
define('DB_PORT', 3306);

We can get all defined constants, including custom constants through get_defined_constants(true) :

 $constants = get_defined_constants(true);
print_r($constants['user']);

2. Comparative analysis

1. Performance comparison

From the perspective of execution efficiency, PHP constants are processed during the compilation stage and are read faster than parsing .env files at runtime (especially when each request is reloaded).

 define('START', microtime(true));
define('CONFIG_VALUE', 'example');

for ($i = 0; $i < 100000; $i++) {
    $x = CONFIG_VALUE;
}
echo 'Time: ' . (microtime(true) - START);

contrast:

 define('START', microtime(true));
putenv('CONFIG_VALUE=example');

for ($i = 0; $i < 100000; $i++) {
    $x = getenv('CONFIG_VALUE');
}
echo 'Time: ' . (microtime(true) - START);

In actual measurement, constant reading is significantly faster.

2. Flexibility and maintainability

The advantage of .env is its variability. Different .env files can be set through different deployment environments without changing the code.

In contrast, constants cannot be modified once defined (unless the script is reloaded), which is not friendly to scenarios where configurations need to be adjusted dynamically.

For example, a service deployed at https://m66.net/api/ requires access addresses to be configured in different environments. The .env file can be very convenient to do this:

 API_URL=https://m66.net/api/

And if you use constants, each time you change the address, you need to redeploy or change the code:

 define('API_URL', 'https://m66.net/api/');

3. Security

.env files should not be exposed to the outside through the web server. If configured properly, their contents will not be visible to the outside. However, if the configuration is improper, there is a risk of leakage.

PHP constants are part of the code and only exist at runtime and cannot be accessed directly by users. As far as the code itself is concerned, constants are more secure.

4. Debugging and visualization

Use get_defined_constants(true)['user'] to easily view all user-defined constants, which is perfect for debugging:

 echo "<pre>";
print_r(get_defined_constants(true)['user']);
echo "</pre>";

However, the content of .env is not easy to track and needs to be read through additional tools or encapsulation.

3. Practical suggestions

4. Conclusion

Whether to use constants to replace .env files depends on project requirements:

• If the project structure is simple and the deployment environment is fixed, using constants can achieve better performance and security.

• If the project involves multi-environment deployment and dynamic configuration loading, the .env file is still a more reasonable choice.

In actual development, it is recommended to use the two in combination: solidify a small number of core configurations in the code in constant form, and save variable or sensitive configurations in .env files to take into account performance, security and flexibility.