PHP 数组避免未定义的偏移量

Question

你好，我有这样的数组

$subject_names[7]="English";
$subject_names[11]="Software Engeneering";

//Student can choose multiple subjects and each subject have int_mark and ext_mark

$results['Matt'][7]['int_mark'] =15;
$results['Matt'][7]['ext_mark'] =55;

$results['Josh'][7]['int_mark'] =12;
$results['Josh'][7]['ext_mark'] =45;
$results['Josh'][11]['int_mark'] =14;
$results['Josh'][11]['ext_mark'] = 52;

// the array is to maintain crosstab format

为了打印这个我做了

echo "Student Name\t";

foreach($subject_names as $subject_name)
{
    echo "$subject_name\t";
}
echo "<br>";

foreach ($results as $student_name => $subjects) 
{
    echo "$student_name\t";

    foreach($subject_names as $subject_id => $sub_name){

        foreach ($subjects[$subject_id] as $mark){ 
             echo "$mark\t";
        }

    }
    echo "<br>";

}

因为学生 "Matt" 没有 subject_id 11 它给我一个错误通知

Notice: Undefined offset: 11

如果学生没有那个主题，我如何忽略它并打印 N/A

感谢您的帮助和建议

Answer 1

您可以将 isset() 与 count() 一起使用：-

if(isset($subjects[$subject_id]) && count($subjects[$subject_id])>0){
    foreach ($subjects[$subject_id] as $mark){ 
       echo "$mark\t";
    }
}

您也可以使用 !empty() 和 count() 检查：-

if(!empty($subjects[$subject_id]) && count($subjects[$subject_id])>0){
    foreach ($subjects[$subject_id] as $mark){ 
       echo "$mark\t";
    }
}

PHP 数组避免未定义的偏移量

PHP array avoid Undefined offset

php

arrays

crosstab