Returns the numeric libcurl error code for the last operation on a handle. This guide demonstrates its use in PHP code and explains when the result or side effect needs extra checks.
What It Does
Returns the numeric libcurl error code for the last operation on a handle.
Syntax and Parameters
The examples below show a real call to curl_errno with suitable arguments. Read the function call in context: its connection, handle, input data or other prerequisites are created before use.
Requirements: cURL extension; HTTP client and transfer-handling tools.
Example 1: Core Behavior
The first case demonstrates the precise handle or result type.
<?php
$ch = curl_init('https://api.example.test/health');
curl_setopt_array($ch, [CURLOPT_RETURNTRANSFER => true, CURLOPT_TIMEOUT => 3, CURLOPT_CONNECTTIMEOUT => 2]);
curl_exec($ch);
echo "cURL error number: " . curl_errno($ch);Observe the returned value or changed resource state. A successful function call can still require additional checks before a higher-level operation is considered successful.
Example 2: Alternative or Failure Case
The second case checks behavior under a different configuration or request.
<?php
$ch = curl_init('https://api.example.test/products');
curl_setopt_array($ch, [CURLOPT_RETURNTRANSFER => true, CURLOPT_TIMEOUT => 4, CURLOPT_CONNECTTIMEOUT => 2]);
curl_exec($ch);
echo "cURL error number: " . curl_errno($ch);Compare the different inputs, environment assumptions or result checks. Do not use a transport-level success value as proof that all business-level requirements were met.
Practical Example: Applying the Rule
The practical case shows how to inspect the operation outcome instead of assuming success.
<?php
$ch = curl_init('https://api.example.test/orders');
curl_setopt_array($ch, [CURLOPT_RETURNTRANSFER => true, CURLOPT_TIMEOUT => 5, CURLOPT_CONNECTTIMEOUT => 2]);
curl_exec($ch);
echo "cURL error number: " . curl_errno($ch);In an application, convert low-level failures into controlled responses and log only non-sensitive diagnostic context.
Important Behavior and Edge Cases
HTTP 404 and 500 are HTTP responses rather than libcurl transport errors unless FAILONERROR is enabled.
TLS validation, bounded timeouts and a destination allowlist are essential for network requests involving potentially untrusted targets.
Comparison with Related Functions or Patterns
| Approach | When it differs |
|---|---|
| curl_errno | Returns the numeric libcurl error code for the last operation on a handle. |
| Related API or pattern | curl_error gives the associated human-readable transport error message. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Mistaking HTTP 404/500 status codes for libcurl transport failures | HTTP 404 and 500 are HTTP responses rather than libcurl transport errors unless FAILONERROR is enabled. |
| Substituting a related API without checking its semantics | curl_error gives the associated human-readable transport error message. |
Key Takeaways
- Returns the numeric libcurl error code for the last operation on a handle.
- HTTP 404 and 500 are HTTP responses rather than libcurl transport errors unless FAILONERROR is enabled.
- curl_error gives the associated human-readable transport error message.
Select this API or pattern based on its documented behavior and the trust boundaries in your own application, and test all external integrations against their actual deployments.