如何通过php用curl调用接口？

<?php 
/**
  * 模拟post进行url请求
  * @param string $url
  * @param array $post_data
  */
 function request_post($url = '',$ispost=true, $post_data = array()) {
  if (empty($url) || empty($post_data)) {
   return false;
  }
  
  $o = "";
  foreach ( $post_data as $k => $v ) 
  { 
   $o.= "$k=" . urlencode( $v ). "&" ;
  }
  $post_data = substr($o,0,-1);
  $key=md5(base64_encode($post_data));
  if($ispost){
   $url=$url;
  }else{
   $url = $url.'?'.$post_data;
  }
  
  
  $curlPost = 'key='.$key;
  header("Content-type: text/html; charset=utf-8");
  $ch = curl_init();//初始化curl
  curl_setopt($ch, CURLOPT_URL,$url);//抓取指定网页
  curl_setopt($ch, CURLOPT_HEADER, 0);//设置header
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);//要求结果为字符串且输出到屏幕上
  if($ispost){
   curl_setopt($ch, CURLOPT_POST, 1);//post提交方式
   curl_setopt($ch, CURLOPT_POSTFIELDS, $curlPost);
  }
  $data = curl_exec($ch);//运行curl
  curl_close($ch);
  return $data;
 }
 ?>

<?php 
require 'ApiModel.php';
function testAction(){
  $url = '接口地址';
  $post_data['appid']  = '10';
  $post_data['appkey']  = 'cmbohpffXVR03nIpkkQXaAA1Vf5nO4nQ';
  $post_data['member_name'] = 'zsjs124';
  $post_data['password'] = '123456';
  $post_data['email'] = 'zsjs124@126.com';
  //$post_data = array();
  $res = request_post($url,$ispost=true,$post_data);  
  print_r($res);

 }
testAction();
?>

<?php 
function serverapi(){
 $key='57173d6ad842d807443ee0db91fed323';
 if($_GET&&$_GET['appkey']=='cmbohpffXVR03nIpkkQXaAA1Vf5nO4nQ'||$_POST&&$_POST['key']===$key){
  $arr=array('name'=>'huanglu','password'=>'123456');
  echo json_encode($arr);
 }else{
  exit('非法访问！');
 }
}
serverapi();
?>