What potential issue arises when multiple processes simultaneously access a PHP script that executes MySQL queries?

When multiple processes simultaneously access a PHP script executing MySQL queries, a potential issue that may arise is race conditions, where the processes interfere with each other and cause unexpected behavior or data corruption. To solve this, you can implement locking mechanisms like mutex or semaphore to ensure that only one process can access the critical section of code at a time. 

<?php

$lockFile = fopen("lock.txt", "w");

if (flock($lockFile, LOCK_EX)) {
    // Critical section of code with MySQL queries
    // ...
    
    flock($lockFile, LOCK_UN);
} else {
    echo "Could not acquire lock.";
}

fclose($lockFile);

?>

Keywords

concurrency race condition database locking transaction isolation deadlock

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