php file_get_contents function easily collects html data_PHP tutorial

//National, the judgment condition is whether $REQUEST_URI contains html
if (!strpos($_SERVER["REQUEST_URI"],".html"))
{
$page="http://qq.ip138.com/weather/";
$html = file_get_contents($page,'r');
$pattern="/Online query of weather trend forecasts for the current day and the next five days in major cities and counties across the country(.*?)< center style="padding:3px">/si";
//html between regular matches
preg_match($pattern,$html,$pg);
echo "";
//regularly replace the remote address with the local address
$p=preg_replace('//weather/(w+)/index.htm/', 'tq.php/$1.html', $pg[1]);
echo $p;
}
//Province, the judgment condition is whether $REQUEST_URI contains?
else if(!strpos($_SERVER["REQUEST_URI"],"?")){
//yoyo recommends using splitting to obtain data. Here is the province name
$province=explode(" /",$_SERVER["REQUEST_URI"]);
$province=explode(".",$province[count($province)-1]);
$province=$province[0];
//What was commented out is the regular expression I wrote myself. I feel it is not well written, but the effect is the same as above
//preg_match('/[^/]+[.(html)]$/', $_SERVER["REQUEST_URI"],$pro);
//$province=preg_replace('/.html/','',$pro[0]);
$page="http:// qq.ip138.com/weather/".$province."/index.htm";
//Try to open the page before obtaining the html data to prevent errors caused by malicious input of addresses
if (!@fopen($ page, "r")) {
die("Sorry, the address does not exist!Click here to return");
exit(0);
}
$html = file_get_contents($page,'r');
$pattern="/Five-day weather trend forecast(.*?) Please enter Enter city/si";
preg_match($pattern,$html,$pg);
echo "";
//Regular replacement, get province, city
$p=preg_replace('/ /weather/(w+)/(w+).htm/', '$2.html?pro=$1', $pg[1]);
echo $p;
}
else {
//City, pass the province through get
$pro=$_REQUEST['pro'];
$city=explode("/",$_SERVER["REQUEST_URI"]);
$city= explode(".",$city[count($city)-1]);
$city=$city[0];
//preg_match('/[^/]+[.(html) ]+[?]/',$_SERVER["REQUEST_URI"],$cit);
//$city=preg_replace('/.html?/','',$cit[0]);
$page="http://qq.ip138.com/weather/".$pro."/".$city.".htm";
if (!@fopen($page, "r") ) {
die("Sorry, the address does not exist!Click here to return");
exit(0);
}
$html = file_get_contents($page,'r');
$pattern="/Five-day weather trend forecast(.*?)Please enter the city/si";
preg_match($pattern,$html,$pg);
echo "";
//Get the real image address
$p=preg_replace('//image//', 'http ://qq.ip138.com/image/', $pg[1]);
echo $p;
}
?>