PHP - 局部变量更改会导致全局更改

Question

我被卡住了，我找不到任何关于这个问题的提法。它不应该发生。全局变量$assignmentInfo被传递给函数，被操作，并作为不同的变量返回。

但是，函数中的局部操作会传播到全局变量，以便下次调用函数时，$assignmentInfo已被更改。每次调用函数时，我想传递相同的，不变的$assignmentInfo版本。

有什么建议吗？

function studentScores($submissionInfo, $assignmentInfo){
    //********************************** Add submission data to assignment data ****************************************************************************
    foreach($assignmentInfo as $assignmentGroup){
        foreach($assignmentGroup->assignments as $assignment){
            foreach($submissionInfo as $submission){
                if(isset($assignment->id) and isset($submission->assignment_id) and $assignment->id == $submission->assignment_id){
                    if (isset($submission->score)){$assignment->score = $submission->score;}
                    if (isset($submission->submitted_at)){$assignment->submitted_at = $submission->submitted_at;}
                    if (isset($submission->workflow_state)){$assignment->workflow_state = $submission->workflow_state;}
                    break;
                }
            }       
        }
    }
    $studentScores = $assignmentInfo;
    return $studentScores;
}

$studentScores = studentScores($submissionInfo->submissions, $assignmentInfo);