Whitelist safe redirect destinations and send Location headers before output, using safe fallbacks when input is invalid.
Before using it, identify which data, connection or runtime state the operation reads or changes. This avoids examples that appear to work but apply to a different context.
How Does This Work?
Whitelist safe redirect destinations and send Location headers before output, using safe fallbacks when input is invalid.
Syntax:
See the complete steps in the practical examples below.
Parameters and Return Value
This is an application workflow rather than one built-in function. Its inputs are request fields, configuration and application state described in each example.
The operation produces an HTTP response or updates application state as shown in the examples.
Example 1: Basic Usage
<?php
$destinationKey = $_GET["page"] ?? "home";
$pages = ["home" => "/", "help" => "/help"];
header("Location: " . ($pages[$destinationKey] ?? "/"), true, 303);Whitelist safe redirect destinations and send Location headers before output, using safe fallbacks when input is invalid.
Example 2: Another Case
<?php
$candidatePath = $_GET["return"] ?? "/";
if (!preg_match('~^/(?!/)[a-z0-9/_-]*$~i', $candidatePath)) { $candidatePath = "/"; }
header("Location: " . $candidatePath, true, 303);The second example changes the input or surrounding conditions, which matters when choosing this API for real application code.
Practical Example
<?php
$allowedDestinations = ["/dashboard", "/profile"];
$destination = $_POST["destination"] ?? "/dashboard";
if (!in_array($destination, $allowedDestinations, true)) { $destination = "/dashboard"; }
header("Location: " . $destination, true, 303);The practical example is a teaching scenario. Change sample configuration and credentials before using a similar design in an application.
Important Behavior and Edge Cases
- Apply authentication, authorization, input limits and failure handling where the workflow crosses trust boundaries.
- Relevant PHP environment: PHP core. Ensure the required extension and operating-system capabilities are present.
- Check results and release resources where necessary; successful syntax alone does not guarantee a successful operation.
Comparison With Related Functions
| Option | When to Use It |
|---|---|
Preventing Open Redirects in PHP | Whitelist safe redirect destinations and send Location headers before output, using safe fallbacks when input is invalid. |
PHP web application design | Use this related operation for its different responsibilities; do not assume identical inputs or return values. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Relying on a single mitigation | Combine validation, authorization, encoding and deployment controls as appropriate. |
| Trusting client-provided state without verification | Revalidate server-side with integrity and replay controls. |
| Exposing secrets in logs or error responses | Return sanitized messages and keep sensitive context in protected systems. |
Key Takeaways
- Whitelist safe redirect destinations and send Location headers before output, using safe fallbacks when input is invalid.
- Apply authentication, authorization, input limits and failure handling where the workflow crosses trust boundaries.
- Validate inputs and handle failure conditions before integrating this operation into a production workflow.
Whitelist safe redirect destinations and send Location headers before output, using safe fallbacks when input is invalid. Use the appropriate runtime and treat any environment-dependent output as an example, not a guaranteed result.