Advertising slots randomly call products

Some time ago, I saw some random advertising pages on my uncle’s website, and I thought they were pretty good.
Let me share, there are mainly three parts, the function part, the advertising code file, and the final function call. The code is as follows:

//Random ad display
function randads(){
$dir="ads"; //Set the directory where records are stored
//$dir="ads"; //Set the directory where records are stored directory
$ads="$dir/ads.txt"; //Set advertising code file
$log ="$dir/ads.log"; //Set ip record file

$ads_lines=file($ads) ;
$lines=count($ads_lines);//The total number of lines in the file

//Read the total number of ads $ads_count and the number of displays into the array $display_array
$ads_count=0;
$display_count=0;
for ($i =0;$i<$lines;$i++){
if((!strcmp(substr($ads_lines[$i],0,7),"display"))){
$ads_count+=1;
$display_array [$ads_count]=substr($ads_lines[$i],8);
$display_count+=$display_array[$ads_count];
}
}
//Decided to randomly display the serial number $display_rand
srand((double)microtime() *1000000);
$display_rand = rand(1,$display_count);

//Determine the advertising serial number $ads_num
$pricount=0;
$ads_num=1;
for($i=1; $i<=$ ads_count; $i++) {
$pricount += $display_array[$i];
if ($display_rand<=$pricount) {$ads_num=$i;break;}
}

//Play ads
$num= 0;
$flag=0;

for($i=0;$i<$lines;$i++){
if((!strcmp(substr($ads_lines[$i],0,7),"display "))){$num++;}
if(($num==$ads_num)and($flag==0)){$flag=1;continue;}
if(($flag==1)and strcmp ($ads_lines[$i][0],"#")){echo $ads_lines[$i];continue;}
if(($flag==1)and(!(strcmp($ads_lines[$i] [0],"#")))){break;}
}
//Record the number of times the ad is displayed
$fp=fopen($log,"a");
fputs($fp,date( "Y-m-d H: i:s " ).getenv("REMOTE_ADDR")."==>".$ads_num."n");
fclose($fp);
}
?>

########Each ad code is separated by '#', display is the display weighting number, the larger the number, the more times it will be displayed #########
### ###########################
display=10



############ ##################
display=10