用php替换所有页面中的字符串

I searched the stack overflow and couldn't find an answer. What I want to do is that I want to replace all the links to switch from http:// to https:// . My public_html contains many folders and files and they also contains more folder and files and so on.

Edit: Also I don't have shell access. I did read some answers but they all used SSH. I cannot download the code so it has to be PHP. Thank you.

Tip: You can turn on force https but that would only work for your server and not for any external resources you download.

This code will replace http: with https: . That's because any prior occurrence of https would result in httpss, that's why the ':' at the end.

<?php
function replacehttp($dir){
    $dir_array = scandir($dir);
    unset($dir_array[array_search('.', $dir_array, true)]);
    unset($dir_array[array_search('..', $dir_array, true)]);
    if (count($dir_array) < 1)
        return;
    foreach($dir_array as $temp){
        if(is_file($dir.'/'.$temp))
        {
         $file_contents = file_get_contents($dir.'/'.$temp);
         $file_contents = str_replace("http:","https:",$file_contents);
         //replacing http: with https: because replacing "http" with "https" would result in existing "https" string to become "httpss"
         file_put_contents($dir.'/'.$temp,$file_contents);  
        }
        if(is_dir($dir.'/'.$temp)) replacehttp($dir.'/'.$temp);
    }
}
replacehttp(getcwd()); //Works in the current directory the php file is placed in or add full path to the directory.
?>