(PHP Extension) Get RSA Key Modulus from .cer or .key

Demonstrates how to get the RSA key modulus from either the certificate (.cer) or RSA key (.key). OpenSSL commands to do the same would be:

openssl x509 -inform DER -in "test.cer"  -modulus -noout 

openssl pkcs8 -inform DER -in​ "test.key"​ -outform PEM -passin pass:"12345​678a​"
   | openssl rsa -inform PEM -modulus -noout 

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

$privKey = new CkPrivateKey();

$password = '12345678a';
$success = $privKey->LoadPkcs8EncryptedFile('qa_data/certs/test_12345678a.key',$password);
if ($success != true) {
    print $privKey->lastErrorText() . "\n";
    exit;
}

$xml = new CkXml();
$xml->LoadXml($privKey->getXml());

// The XML contains the parts of the key in base64.
print 'Private Key XML:' . "\n";
print $xml->getXml() . "\n";

// We can get the base64 modulus like this:
$modulus = $xml->getChildContent('Modulus');
print 'base64 modulus = ' . $modulus . "\n";

// To convert to hex:
$binDat = new CkBinData();
$binDat->AppendEncoded($modulus,'base64');
$hexModulus = $binDat->getEncoded('hex');
print 'hex modulus = ' . $hexModulus . "\n";

// Now get the modulus from the cert:
$cert = new CkCert();

$success = $cert->LoadFromFile('qa_data/certs/test_12345678a.cer');
if ($success != true) {
    print $cert->lastErrorText() . "\n";
    exit;
}

// The cert contains the public key, which is composed of the
// modulus + exponent (for RSA keys).
// pubKey is a CkPublicKey
$pubKey = $cert->ExportPublicKey();

$xml->LoadXml($pubKey->getXml());
print 'Public Key XML:' . "\n";
print $xml->getXml() . "\n";

// Proceed in the same way as before....
$modulus = $xml->getChildContent('Modulus');
print 'base64 modulus = ' . $modulus . "\n";

// To convert to hex:
$binDat->Clear();
$binDat->AppendEncoded($modulus,'base64');
$hexModulus = $binDat->getEncoded('hex');
print 'hex modulus = ' . $hexModulus . "\n";


?>