<?php // http://stackoverflow.com/questions/37719160/compare-the-data-of-two-csv-file
      // https://i...content-available-to-author-only...e.com/uZnCVb
      

$srcText = "Hello World! - " . uniqid();
$key    = 's7aBkf4Ypn59bWviQziPDXyPasdaYlhQ';

$srcEncrypted  = '';
$srcDecrypted  = '';

$srcEncrypted = encrypt($srcText, $key);

$srcDecrypted = decrypt($srcEncrypted, $key);

var_dump($srcText, 
         $srcEncrypted, 
         $srcDecrypted, 
         $srcDecrypted == $srcText);
         
exit(__FILE__.__LINE__);


/**
 * Encrypt a string
 * 
 * Include the exact length of the data string so we can return the exact length
 * after the decryption.
 *     
 * @Param string $data 
 * @Param string $key
 * 
 * @return string  - base64_encoded   
 */ 
function encrypt($data, $key) {

  $cypher = $cypher = 'aes-256-cbc';  
  $ivSize  = openssl_cipher_iv_length($cypher);
  $ivData  = openssl_random_pseudo_bytes($ivSize);
  
  $encripted = openssl_encrypt($data, 
                              $cypher, 
                              $key, 
                              // USE THIS ONLY !!!!
                              OPENSSL_RAW_DATA, 
                              $ivData);

                            
  return base64_encode($ivData  . $encripted);
}


/**
 * Decrypt a string
 * 
 * @Param string $data 
 * @Param string $key
 * 
 * @return string  - original text   
 */ 
function decrypt($data, $key) {

  $cypher = 'aes-256-cbc';  
  $ivSize  = openssl_cipher_iv_length($cypher);

  $data = base64_decode($data);
  $ivData   = substr($data, 0, $ivSize);
   
  $encData = substr($data, $ivSize);

  $output = openssl_decrypt($encData, 
                            $cypher, 
                            $key, 
                            OPENSSL_RAW_DATA, 
                            $ivData);
  return $output;
}