Prohibition of parallel (simultaneously launched n times) execution of a php script?

Question

PHP

Good day everyone. The problem is this:
With the help of something, the user can simultaneously run the same php script n number of times.
The script at one time looks at the number of records in the table, filtering by the current user, writes to the variable “A”, adds a new record to the table and simply adds +1 to the variable “A”. Well, he continues to do his job.
But when the script is run n times at the same time, the result of the variable "A" is the same, hence the number of records, because everyone looked at the same time.
How to avoid it? So that until one of the scripts is executed, the others are waiting, well, or something like that.

Answer 1

transaction

Answer 2

Read a variable from a file, and write to the file with a lock:

function autoinc_id($dataset="common",$min=0) {
    $file = __DIR__ . "/autoinc.json";
    $fp = fopen($file, 'c+');
    flock($fp, LOCK_SH);
    $json = json_decode(file_get_contents($file),true);
    if (!isset($json[$dataset])) {
    $json[$dataset]=$min;
  } else {
    if ($json[$dataset]<$min) {$json[$dataset]=$min;} else {$json[$dataset]++;}
  }
  file_put_contents($file,json_encode($json));
    flock($fp, LOCK_UN);
    fclose($fp);
    return $json[$dataset];
}