Restrict outbound request destinations, protect against redirects and DNS changes, and block internal, loopback and metadata-service addresses.
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?
Restrict outbound request destinations, protect against redirects and DNS changes, and block internal, loopback and metadata-service addresses.
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
$host = parse_url("https://public.example.test/resource", PHP_URL_HOST);
if ($host === null || $host === false) { throw new InvalidArgumentException("Invalid host"); }
// A complete implementation also validates all DNS answers at connection time.Restrict outbound request destinations, protect against redirects and DNS changes, and block internal, loopback and metadata-service addresses.
Example 2: Another Case
<?php
$url = "https://public.example.test/data.json";
$scheme = parse_url($url, PHP_URL_SCHEME);
if ($scheme !== "https") { throw new InvalidArgumentException("HTTPS required"); }
// Protocol checks alone do not prevent SSRF.The second example changes the input or surrounding conditions, which matters when choosing this API for real application code.
Practical Example
<?php
$curlHandle = curl_init("https://public.example.test/api");
curl_setopt_array($curlHandle, [CURLOPT_PROTOCOLS_STR => "https", CURLOPT_FOLLOWLOCATION => false, CURLOPT_TIMEOUT => 5]);
// Restrict DNS resolution and outgoing IP targets separately.
curl_close($curlHandle);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 Server-Side Request Forgery | Restrict outbound request destinations, protect against redirects and DNS changes, and block internal, loopback and metadata-service addresses. |
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
- Restrict outbound request destinations, protect against redirects and DNS changes, and block internal, loopback and metadata-service addresses.
- 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.
Restrict outbound request destinations, protect against redirects and DNS changes, and block internal, loopback and metadata-service addresses. Use the appropriate runtime and treat any environment-dependent output as an example, not a guaranteed result.