php http_build_query stream_context_create post请求

<?php
function send_post($url, $post_data)
{
    $postdata = http_build_query($post_data);
    $options = array(
        'http' => array(
            'method' => 'POST',
            'header' => 'Content-type:application/x-www-form-urlencoded',
            'content' => $postdata,
            'timeout' => 15 * 60 // 超时时间（单位:s）
        )
    );
    $context = stream_context_create($options);
    $result = file_get_contents($url, false, $context);

    echo $result;
}

//使用方法
$post_data = array(
    'a' => '11',
    'b' => '22'
);
send_post('http://localhost/b.php', $post_data);