$config = array( 
  //"digest_alg" => "sha512", 
  "private_key_bits" => 512,           //字节数  512 1024 2048  4096 等 
  "private_key_type" => OPENSSL_KEYTYPE_RSA,   //加密类型 
); 
   
//1.创建公钥和私钥  返回资源 
$res = openssl_pkey_new($config); 
 
//从得到的资源中获取私钥  并把私钥赋给$privKey
openssl_pkey_export($res, $privKey); 
 
//从得到的资源中获取私钥  并把私钥赋给$pubKey
$pubKey = openssl_pkey_get_details($res); 
 
$pubKey = $pubKey["key"]; 
var_dump(array('privKey'=>$privKey,'pubKey'=>$pubKey)); 
die; 

//2.加密解密数据 要加密的数据 
$data = 'plaintext data goes here';             

//对$data进行加密 要加密的数据字符串 得到加密后的数据 加密所需要的公钥
openssl_public_encrypt($data, $encrypted, $pubKey); 
echo base64_encode($encrypted); 
 
//对加密后的数据进行解密 解密的数据 得到解密后的数据 解密所需要的私钥
$decrypted = base64_decode($encrypted);
openssl_private_decrypt($encrypted, $decrypted, $privKey); 
echo $decrypted;  

//3.一个加密解密类 
class rsa { 
  private $public_key = ''; //公密钥 
  private $private_key = ''; //私密钥 
  private $public_key_resource = ''; //公密钥资源 
  private $private_key_resource = ''; //私密钥资源 
  /** 
   * 架构函数 
   * @param [string] $public_key_file [公密钥文件地址] 
   * @param [string] $private_key_file [私密钥文件地址] 
   */ 
  public function __construct($public_key,$private_key) { 
    $this->public_key = $public_key;   
 $this->private_key = $private_key;
 
 if(false == ($this->public_key_resource = $this->is_bad_public_key($this->public_key)) || false == ($this->private_key_resource = $this->is_bad_private_key($this->private_key))) { 
  throw new Exception('public key or private key no usable'); 
 } 
  } 
  private function is_bad_public_key($public_key) { 
    return openssl_pkey_get_public($public_key); 
  } 
  private function is_bad_private_key($private_key) { 
    return openssl_pkey_get_private($private_key); 
  } 
  /** 
   * 生成一对公私密钥 成功返回 公私密钥数组 失败 返回 false 
   */ 
  public function create_key() { 
    $res = openssl_pkey_new(); 
    if($res == false) return false; 
    openssl_pkey_export($res, $private_key); 
    $public_key = openssl_pkey_get_details($res); 
    return array('public_key'=>$public_key["key"],'private_key'=>$private_key); 
  } 
  /** 
   * 用私密钥加密 
   */ 
  public function private_encrypt($input) { 
    openssl_private_encrypt($input,$output,$this->private_key_resource); 
    return base64_encode($output); 
  } 
  /** 
   * 解密 私密钥加密后的密文 
   */ 
  public function public_decrypt($input) { 
    openssl_public_decrypt(base64_decode($input),$output,$this->public_key_resource); 
    return $output; 
  } 
  /** 
   * 用公密钥加密 
   */ 
  public function public_encrypt($input) { 
    openssl_public_encrypt($input,$output,$this->public_key_resource); 
    return base64_encode($output); 
  } 
  /** 
   * 解密 公密钥加密后的密文 
   */ 
  public function private_decrypt($input) { 
    openssl_private_decrypt(base64_decode($input),$output,$this->private_key_resource); 
    return $output; 
  } 
} 

$private_key = '-----BEGIN RSA PRIVATE KEY----- 
MIICXQIBAAKBgQC3//sR2tXw0wrC2DySx8vNGlqt3Y7ldU9+LBLI6e1KS5lfc5jl 
TGF7KBTSkCHBM3ouEHWqp1ZJ85iJe59aF5gIB2klBd6h4wrbbHA2XE1sq21ykja/ 
Gqx7/IRia3zQfxGv/qEkyGOx+XALVoOlZqDwh76o2n1vP1D+tD3amHsK7QIDAQAB 
AoGBAKH14bMitESqD4PYwODWmy7rrrvyFPEnJJTECLjvKB7IkrVxVDkp1XiJnGKH 
2h5syHQ5qslPSGYJ1M/XkDnGINwaLVHVD3BoKKgKg1bZn7ao5pXT+herqxaVwWs6 
ga63yVSIC8jcODxiuvxJnUMQRLaqoF6aUb/2VWc2T5MDmxLhAkEA3pwGpvXgLiWL 
3h7QLYZLrLrbFRuRN4CYl4UYaAKokkAvZly04Glle8ycgOc2DzL4eiL4l/+x/gaq 
deJU/cHLRQJBANOZY0mEoVkwhU4bScSdnfM6usQowYBEwHYYh/OTv1a3SqcCE1f+ 
qbAclCqeNiHajCcDmgYJ53LfIgyv0wCS54kCQAXaPkaHclRkQlAdqUV5IWYyJ25f 
oiq+Y8SgCCs73qixrU1YpJy9yKA/meG9smsl4Oh9IOIGI+zUygh9YdSmEq0CQQC2 
4G3IP2G3lNDRdZIm5NZ7PfnmyRabxk/UgVUWdk47IwTZHFkdhxKfC8QepUhBsAHL 
QjifGXY4eJKUBm3FpDGJAkAFwUxYssiJjvrHwnHFbg0rFkvvY63OSmnRxiL4X6EY 
yI9lblCsyfpl25l7l5zmJrAHn45zAiOoBrWqpM5edu7c 
-----END RSA PRIVATE KEY-----';

$public_key = '-----BEGIN PUBLIC KEY----- 
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC3//sR2tXw0wrC2DySx8vNGlqt 
3Y7ldU9+LBLI6e1KS5lfc5jlTGF7KBTSkCHBM3ouEHWqp1ZJ85iJe59aF5gIB2kl 
Bd6h4wrbbHA2XE1sq21ykja/Gqx7/IRia3zQfxGv/qEkyGOx+XALVoOlZqDwh76o 
2n1vP1D+tD3amHsK7QIDAQAB 
-----END PUBLIC KEY-----';

$rsa = new rsa($public_key,$private_key);  
$str = '加密解密'; 
$str = $rsa->public_encrypt($str); //用公密钥加密 
echo $str,'</br>'; 
$str = $rsa->private_decrypt($str); //用私密钥解密 
echo $str,'</br>'; 
//============================================================= 
$str = $rsa->private_encrypt($str); //用私密钥加密 
echo $str,'</br>'; 
$str = $rsa->public_decrypt($str); //用公密钥解密 
echo $str,'</br>';