<?php
$subject = array(
"commonName" => "example.com",
);
$private_key = openssl_pkey_new(array(
"private_key_bits" => 2048,
"private_key_type" => OPENSSL_KEYTYPE_RSA,
));
$csr = openssl_csr_new($subject, $private_key, array('digest_alg' => 'sha384') );
openssl_pkey_export_to_file($private_key, 'example-priv.key');
// Along with the subject, the CSR contains the public key corresponding to the private key
openssl_csr_export_to_file($csr, 'example-csr.pem');
?>