$file = file_put_contents('data.txt', "text to write to file - 1" . PHP_EOL, FILE_APPEND | LOCK_EX);
$file = file_put_contents('data.txt', "text to write to file - 2" . PHP_EOL, FILE_APPEND | LOCK_EX);
$file = file_put_contents('data.txt', "text to write to file - 3" . PHP_EOL, FILE_APPEND | LOCK_EX);
/*
run:
text to write to file - 1
text to write to file - 2
text to write to file - 3
*/