$_ENV

Environment variables let deployments configure secrets and service endpoints without hard-coding them in source. Availability through $_ENV depends on PHP configuration; getenv is another interface. Use a configuration library or framework, never commit real credentials, and provide safe defaults only for non-secret development settings. Avoid printing environment values into logs or HTTP responses. Further guidance Superglobal values come from the request or process environment and can be missing or have an unexpected type. Check the key and shape before use, validate it for the operation, and avoid printing secrets or trusting client-controlled headers. Prefer the specific input source over merged request data. Practice task: Create a fresh example for $_ENV. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.