<?php
$url = ‘http://www.baidu.com/link?url=77I2GJqjJ4zBBpC8yDF8xDhiqDSn1JZjFWsHhEoSNd85PkV8Xil-rckpQ8_kjGKNNq‘;
function fileExists($url){
    stream_context_set_default(
        array(
            ‘http‘ => array(
                ‘timeout‘ => 5,
            )
        )
    );
    $header = get_headers($url,1);
    if(strpos($header[0],‘200‘)){
        return true;
    }
    if(strpos($header[0],‘404‘)){
        return false;
    }
    if (strpos($header[0],‘301‘) || strpos($header[0],‘302‘)) {
        if(is_array($header[‘Location‘])) {
            $redirectUrl = $header[‘Location‘][count($header[‘Location‘])-1];
        }else{
            $redirectUrl = $header[‘Location‘];
        }
        return fileExists($redirectUrl);
    }
}

var_dump(fileExists($url));