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)
openssl_csr_get_public_key — 返回CSR的公钥
openssl_csr_get_public_key() 从csr中提取公钥供其他功能使用。
成功，返回一个私钥标识符，错误则返回FALSE.
Example #1 openssl_csr_get_public_key() example
<?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' => 'sha256') );
$public_key = openssl_csr_get_public_key($csr);
$info = openssl_pkey_get_details($public_key);
echo $info['key'];
?>
Function openssl_pkey_get_details can read this resource. Try:
<?php
print_r(openssl_pkey_get_details(openssl_csr_get_public_key($csr)));
?>