Why am I getting an 'SSL certificate problem: unable to get local issuer certificate' error when using cURL with the PayPal Access API?

Troubleshooting SSL Certificate Errors with PayPal Access API in cURL

When using cURL in PHP to make requests to the PayPal Access API endpoint, an SSL certificate issue may arise, resulting in the error message "SSL certificate problem: unable to get local issuer certificate." This error can hinder access to the API and hinder token retrieval.

To resolve this issue, it's crucial to understand the role of SSL certificates in securing the connection with the API. PayPal Access API requires SSL to ensure data encryption and protect user information.

1) Do I need SSL to use PayPal Access if I only need to get the user email?

Yes, SSL is necessary for using the PayPal Access API, regardless of the scope of data access. The API mandates SSL to safeguard user information and maintain the confidentiality of financial data.

2) If I don't need SSL, why does this error occur?

The error occurs even when SSL is not explicitly required because cURL checks the system CA certificates by default. If the cURL version you're using has an outdated or missing list of trusted certificate authorities, it will fail to validate PayPal's certificate and trigger the error.

Solution

To resolve the issue, you need to update your PHP configuration with the correct SSL certificate authority bundle. Here's how:

1. Download the current list of certificate authority (CA) certificates from a trusted source (e.g., https://curl.se/docs/caextract.html).
2. Save the file (cacert.pem) in a secure location.
3. Edit your php.ini file and add the following line:

curl.cainfo=<path-to-cacert.pem>

For example:

curl.cainfo=/var/www/html/cacert.pem

4. Restart your web server to apply the changes.

Once these steps are complete, cURL will use the updated CA bundle to validate PayPal's certificate, allowing you to successfully make requests and retrieve the user email.

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