How to split and merge files in PHP breakpoint resume_PHP tutorial

ini_set("memory_limit", "50M");//required Yes, try to make it as large as possible according to the actual situation of your environment to prevent errors
ini_set("max_execution_time", "100");
//file_exists() function checks whether the file or directory exists, returns true if it exists, otherwise returns false.
//fread() function reads files (safe for binary files). fread() reads up to length bytes from the file pointer file.
//filesize() function returns the size (bytes) of the specified file. The results of this function will be cached. Please use clearstatcache() to clear the cache.
$orgFile = 'Fireworks8-chs.exe';//Source file
$cacheFileName = 'vbcache';//Split into temporary file blocks
function cutFile($fileName,$block) {/ /split
global $cacheFileName;
if (!file_exists($fileName)) return false;
$num = 1;
$file = fopen($fileName, 'rb');
while ($content = fread($file,$block)) {
$cacheFile = $cacheFileName . $num++ . '.dat';
$cfile = fopen($cacheFile, 'wb');
fwrite($cfile, $content);
fclose($cfile);
}
fclose($file);
}
function mergeFile($targetFile) {//Merge
global $cacheFileName;
$num = 1;
$file = fopen($targetFile, 'wb');
while ($num > 0) {
$cacheFile = $ cacheFileName . $num++ . '.dat';
if (file_exists($cacheFile)) {
$cfile = fopen($cacheFile, 'rb');
$content = fread($cfile, filesize ($cacheFile));
fclose($cfile);
fwrite($file, $content);
}
else {
$num = -1;
}
}
fclose($file);
}
//Call
cutFile($orgFile, 10 * pow(2,20)); //10 * pow(2,20) It is equal to 10M. The pow() function returns x raised to the yth power
mergeFile('ok.exe');
?>