class Solution param Integer $obstacles return Integer function binarySearch$arr $target $left = 0; $right = count$arr - 1; while $left = $right $mid = $left + $right - $lef

The error occurred because the binarySearch function is not defined within the Solution class. To fix this, you can either define the binarySearch function within the Solution class or move it outside the class and call it as a standalone function.

Here's an updated version of the code with the binarySearch function defined within the Solution class:

class Solution {
    /**
     * @param Integer[] $obstacles
     * @return Integer[]
     */
    function binarySearch($arr, $target) {
        $left = 0;
        $right = count($arr) - 1;
        while ($left <= $right) {
            $mid = $left + ($right - $left >> 1);
            if ($arr[$mid] <= $target) $left = $mid + 1;
            else $right = $mid - 1;
        }
        return $left;
    }
    
    function longestObstacleCourseAtEachPosition($obstacles) {
        $ans = array();
        $dp = array();
        for ($i = 0; $i < count($obstacles); $i++) {
            $v = $obstacles[$i];
            $p = $this->binarySearch($dp, $v+1);
            if ($p < count($dp)) $dp[$p] = $v;
            else $dp[] = $v;
            $ans[] = $p + 1;
        }
        return $ans;
    }
}

Now, you should be able to call the longestObstacleCourseAtEachPosition method without any errors