html - How to create increment folder name in php

Example:

$max=0;
$files=scandir("/path/to/your/output-directory");
$matches=[];
foreach($files as $file){
    if(preg_match("/folder(\d+)/", $file, $matches){
        $number=intval($matches[1]);
        if($number>$max)
            $max=$number;
    }
}
$newNumber=$max+1;
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That is a simple example to get you the next number. There are many other factors to consider. For instance, what happens if two users submit the form concurrently? You would need some synchronization metaphor(such as semaphore or file lock) to ensure only insert can occur at a time.

You could use a separate lock file to store the current number and function as a synchronization method.

I would highly encourage finding a different way to store the data. Using a database to store this data may be a better option.

Here is a more complete example for sequentially creating directories using a lock file for the sequence and synchronization. This omits some error handling that should be added for production code, but should provide the core functionality.

define("LOCK_FILE", "/some/file/path"); //A file for synchronization and to store the counter
define("OUTPUT_DIRECTORY", "/some/directory"); //The directory where you want to write your folders

//Open the lock file
$file=fopen(LOCK_FILE, "r+");
if(flock($file, LOCK_EX)){
    //Read the current value of the file, if empty, default to 0
    $last=fgets($file);
    if(empty($last))
        $last=0;
    //Increment to get the current ID
    $current=$last+1;
    //Write over the existing value(a larger number will always completely overwrite a smaller number written from the same position)
    rewind($file);
    fwrite($file, (string)$current);
    fflush($file);
    //Determine the path for the next directory
    $dir=OUTPUT_DIRECTORY."/folder$current";
    if(file_exists($dir))
        die("Directory $dir already exists. Lock may have been reset");
    //Create the next directory
    mkdir($dir);
    //TODO: Write your content to $dir (You'll need to provide this piece)
    //Release the lock
    flock($file, LOCK_UN);
}
else{
    die("Unable to acquire lock");
}
//Always close the file handle
fclose($file);
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