Function openssl_pkey_get_details can read this resource. Try:
<?php
print_r(openssl_pkey_get_details(openssl_csr_get_public_key($csr)));
?>
(PHP 5 >= 5.2.0, PHP 7, PHP 8)
openssl_csr_get_public_key — Devuelve la clave púbilca de un CERT
Function openssl_pkey_get_details can read this resource. Try:
<?php
print_r(openssl_pkey_get_details(openssl_csr_get_public_key($csr)));
?>