SSL encryption, decryption, verification, and signature methods under PHP (super simple)

function sign($data) {
 //读取私钥文件
 $priKey = file_get_contents('key/rsa_private_key.pem');
 
 //转换为openssl密钥，必须是没有经过pkcs8转换的私钥
 $res = openssl_get_privatekey($priKey);
 
 //调用openssl内置签名方法，生成签名$sign
 openssl_sign($data, $sign, $res);
 
 //释放资源
 openssl_free_key($res);
 
 return $sign;
}

function verify($data, $sign) {
 //读取支付宝公钥文件
 $pubKey = file_get_contents('key/alipay_public_key.pem');
 
 //转换为openssl格式密钥
 $res = openssl_get_publickey($pubKey);
 
 //调用openssl内置方法验签，返回bool值
 $result = (bool)openssl_verify($data, $sign, $res);
  
 //释放资源
 openssl_free_key($res);
 
 return $result;

function decrypt($content) {
 
 //读取商户私钥
 $priKey = file_get_contents('key/rsa_private_key.pem');
  
 //转换为openssl密钥，必须是没有经过pkcs8转换的私钥
 $res = openssl_get_privatekey($priKey);
 
 //声明明文字符串变量
 $result = '';
 
 //循环按照128位解密
 for($i = 0; $i < strlen($content)/128; $i++ ) {
  $data = substr($content, $i * 128, 128);
   
 //拆分开长度为128的字符串片段通过私钥进行解密，返回$decrypt解析后的明文
  openssl_private_decrypt($data, $decrypt, $res);
 
 //明文片段拼接
  $result .= $decrypt;
 }
 
 //释放资源
 openssl_free_key($res);
 
 //返回明文
 return $result;
}