Securely encode / encrypt and decode / decrypt a string using PHP.

First, you'll need to set up two functions—one for encryption and another for decryption. We'll use AES-256-CBC for encryption, which is a strong cipher, and you'll need to specify a secret key and an initialization vector.

<?php


function encrypt_data($data, $key='rizi_farhan_web404', $iv='1234567890123456') { 
/* $key = ;  // Ensure this key is kept secret $iv =   // 16 bytes initialization vector */
    $encrypted = openssl_encrypt($data, 'aes-256-cbc', $key, 0, $iv);
    return str_replace(array('+', '/'), array('-', '_'), base64_encode($encrypted));  // URL-safe encoding
}

function decrypt_data($data, $key='rizi_farhan_web404', $iv='1234567890123456') {
    $data = base64_decode(str_replace(array('-', '_'), array('+', '/'), $data));  // URL-safe decoding
    return openssl_decrypt($data, 'aes-256-cbc', $key, 0, $iv);
}

// Testing the functions
$originalID = 'Solmate';
$encryptedID = encrypt_data($originalID);
$decryptedID = decrypt_data($encryptedID);

echo "Original ID: $originalID\n";
echo "Encrypted ID: $encryptedID\n";
echo "Decrypted ID: $decryptedID\n";
?>

Output:

Original ID: Solmate Encrypted ID: ajVFV09UMmRoV2tvc0xXQnk5dVQ0dz09 Decrypted ID: Solmate

Key and IV: The key should be a 256-bit key for AES-256 encryption, and the initialization vector (IV) should be 16 bytes. Make sure to keep the key secure and consistent across your application to be able to decrypt the data.