symmetric_class_included.php

<?php

error_reporting(E_ALL);
ini_set('display_errors', '1');

class Encryption
{
	const CIPHER = MCRYPT_RIJNDAEL_128; // Rijndael-128 is AES
	const MODE   = MCRYPT_MODE_CBC;

	/* Cryptographic key of length 16, 24 or 32. NOT a password! */
	private $key;
	
	
	private $init = 0;
	private $how_many_per_block; //chars; //every block will be a line

	
	public function __construct($key) {
		$this->key = $key;
		
		
		$this->how_many_per_block = 1024; //chars; //every block will be a line
		
	}

	public function encrypt($plaintext) {
		$ivSize = mcrypt_get_iv_size(self::CIPHER, self::MODE);
		$iv = mcrypt_create_iv($ivSize, MCRYPT_DEV_URANDOM);
		$ciphertext = mcrypt_encrypt(self::CIPHER, $this->key, $plaintext, self::MODE, $iv);
		return base64_encode($iv.$ciphertext);
	}

	public function decrypt($ciphertext) {
		$ciphertext = base64_decode($ciphertext);
		$ivSize = mcrypt_get_iv_size(self::CIPHER, self::MODE);
		if (strlen($ciphertext) < $ivSize) {
			throw new Exception('Missing initialization vector');
		}

		$iv = substr($ciphertext, 0, $ivSize);
		$ciphertext = substr($ciphertext, $ivSize);
		$plaintext = mcrypt_decrypt(self::CIPHER, $this->key, $ciphertext, self::MODE, $iv);
		return rtrim($plaintext, "\0");
	}


	public function encrypt_file($file_to_encrypt,$encrypted_file,&$error){

		$data = file_get_contents($file_to_encrypt);;
		if(!$data){
			$error = 'No data';
			return false;
		} 

		if(!file_exists($file_to_encrypt)){
			$error = 'no file to encrypt';	
			return false;
		} 
		if(file_exists($encrypted_file)) unlink($encrypted_file);

		$final_encrypted_string ="";
		$total = strlen($data);
		
		$init = 0;
		$how_many_per_block = $this->how_many_per_block;
		do{
			$partial_encrypted="";
			$last_one = false;
			if($init+$how_many_per_block>$total){
				$how_many_per_block = $total-$init;
				$last_one = true;
			} 	
			$partial_string = substr($data,$init,$how_many_per_block);	
			$partial_encrypted = $this->encrypt(base64_encode($partial_string));
			file_put_contents($encrypted_file, ($partial_encrypted.PHP_EOL),FILE_APPEND);	
			$final_encrypted_string.=$partial_encrypted.'\n';
			$init+=$how_many_per_block;
		}while(!$last_one);

		return true;
	}

	public function decrypt_file($encrypted_file,$encrypted_decrypted_file,&$error){


		if(file_exists($encrypted_decrypted_file)) unlink($encrypted_decrypted_file);
		if(!file_exists($encrypted_file)){
			$error = 'No file to decrypt';
			return false;
		} 
		$file = fopen($encrypted_file, "r");
		if ($file) {
			while(!feof($file)){
				$line = fgets($file);		
				if(!$line) continue;
				
				$decrypted = $this->decrypt($line);
				$decrypted = base64_decode($decrypted);
				file_put_contents($encrypted_decrypted_file, $decrypted,FILE_APPEND);
			}
			fclose($file);
		} else {
			// error opening the file.
		} 
		return true;

	}

}


$file_to_encrypt = 'file_to_encrypt_big.txt';;
$encrypted_file='file_to_encrypt_encrypted.txt';
$encrypted_decrypted_file = 'file_to_encrypt_encrypted_decrypted.txt';



$key = 'this is my key';
$crypt = new Encryption($key);

$error = "";
$res = $crypt->encrypt_file($file_to_encrypt,$encrypted_file,$error);
if(!$res) die('ERROR encrypting: '.$error);
$res =$crypt->decrypt_file($encrypted_file,$encrypted_decrypted_file,$error);
if(!$res) die('ERROR decrypting: '.$error);