php异步调用方法

正常情况下，PHP执行的都是同步请求，代码自上而下依次执行，但有些场景如发送邮件、执行耗时任务等操作时就不适用于同步请求，只能使用异步处理请求。

<?php
function connect($host, $url)
{
    // check whether the curl function is exist or not.
    if (function_exists('curl_version')) {
        connectCurl($host, $url);
        return;
    }

    // default
    connectFwrite($host, $url);
    return;
}


function connectCurl($host, $url)
{
    $ch = curl_init(); 
    curl_setopt($ch, CURLOPT_URL, "http://" . $host . '/' . $url); 
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_0);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: close'));
    curl_setopt($ch, CURLOPT_TIMEOUT, 2); 
    $response = curl_exec($ch); 
    
    curl_close($ch);
}


function connectFwrite($host, $url)
{
    $fp = @fsockopen($host, 80, $errorNum, $errorStr);

    if (!$fp) {
        echo 'There was an error connecting to the site.';
        exit;
    }

    $request = "GET /" . $url . " HTTP/1.1\r\n";
    $request .= "Host: " . $host . "\r\n";
    $request .= "Connection: Close\r\n\r\n";

    fwrite($fp, $request);

    fclose($fp);
}

$host="";
$url ="";
connect($host, $url);
echo "Cronjob processed.\r\n";
return;

最后在用crontab设置定时访问一下这个文件就可以达到效果!