Asymmetric Encryption - encrypt data via public and decrypt via private key

asymmetric_encryption.php

<?php

/**
 * Create private key:
 * $ openssl genrsa -out private.key 2048
 *
 * Create public key:
 * $ openssl rsa -in private.key -outform PEM -pubout -out public.pem
 */

$privateKey = openssl_get_privatekey( file_get_contents( 'private.key' ) );
$publicKey  = openssl_get_publickey( file_get_contents( 'public.pem' ) );
$data       = 'ThisIsAn$Encrypted(Password';

echo "# Data in:\n$data\n\n";

$encrypted = $e = null;
openssl_seal( $data, $encrypted, $e, [ $publicKey ] );

$sealedData = base64_encode( $encrypted );
$envelope   = base64_encode( $e[0] );

echo "# Sealed data:\n$sealedData\n\n";
echo "# Envelope:\n$envelope\n\n";

$input     = base64_decode( $sealedData );
$eInput    = base64_decode( $envelope );
$plaintext = null;

openssl_open( $input, $plaintext, $eInput, $privateKey );

echo "# Data out:\n$plaintext\n";

echo "- - - - - - - - - - - - - - - - - -\n\n";

// Something to encrypt
$text = 'This is the text to encrypt';
echo "# This is the original text:\n$text\n\n";

// Encrypt using the public key
openssl_public_encrypt( $text, $encrypted, $publicKey );

$encrypted_hex = bin2hex( $encrypted );
$encryptedBase64 = base64_encode( $encrypted );
echo "This is the encrypted text:\n$encrypted_hex\n\n";
echo "This is the encrypted text (base64):\n$encryptedBase64\n\n";

// Decrypt the data using the private key
openssl_private_decrypt( base64_decode( $encryptedBase64 ), $decrypted, $privateKey );

echo "This is the decrypted text: $decrypted\n\n";