for ($i=0, $_l = strlen($movement); $i < $_l; $i++) {
    $movement[$i] == ')' ? $floor-- : $floor++;
}

/tmp/phpadvent/src/day1 master*
❯ for f in part*; do echo "$f"; php "$f"; echo ""; done;
part1.php
138
Total Execution Time: 0.001763

part2.php
Floor: 138
Basement Position: 1770
Total Execution Time: 0.001976

part3.php
Final floor: 138
Total Execution Time: 0.000812