working solution:

• Assuming On windows

XAMPP server

similar for other environment – download and extract for cacert.pem here (a clean file format/data)

https://gist.github.com/VersatilityWerks/5719158/download

• put it here

C:\xampp\php\extras\ssl\cacert.pem

• in your php.ini put this line in this section:

;;;;;;;;;;;;;;;;;;;;
; php.ini Options  ;
;;;;;;;;;;;;;;;;;;;;

curl.cainfo = "C:\xampp\php\extras\ssl\cacert.pem"

• restart your webserver/apache

Problem solved!

(source: https://laracasts.com/discuss/channels/general-discussion/curl-error-60-ssl-certificate-problem-unable-to-get-local-issuer-certificate)