PHP, XML，回显时重复属性的问题

我已经弄明白了，花了我好几个小时，但我终于弄明白了。

这是我用于PHP的代码，XML保持不变。我会尽量详细，这样它就可以帮助任何人有类似的问题，或者这样他们就可以从中提取信息并修改它，以满足他们的需要。

<?php
//self explanatory
$xml = DOMDocument::load('examdata.xml');
//again, self explanatory
$xpath = new DOMXPath($xml);
//looks for ex under exam in the xml I loaded above xml
$exams = $xpath->query('//exam/ex');
//I just put a number for testing purposes but it actually gets the user's exam id from the database
$studentexnum = "5";
//column counter, will be used to tell that after every 2 chapters, break the table data (td) and table row (tr) and create a new one
$_2chapters = 1;
//Opens the table and displays it to the client
echo "<table cellpadding='"5'" cellspacing='"5'" border='"0'" width='"25%'" align='"center'">
    <tr>"; //Opens the first table row and end the echoing
//starts the loop, for every exam, makes exam2 same as exam
foreach($exams as $exams2) {
//looks at my xml file for the tag ex (what I defined above) and gets the attribute called chapter from his parent (the tag above it)
    $chapter = $exams2->parentNode->getAttribute('chapter');
//gets the attribute called id from the tag ex
    $examid = $exams2->getAttribute('id');
//makes the tag ex a string so we could display it
    $examname = $exams2->nodeValue;
////////////////////////////////////////Now for the Fun Part/////////////////////////////////////////////////////////////////////////////////
//conditional statement saying that if the variable chapter2 is set, display the conditions below, if it's not set (which is not when its starts the loop) do something else
    if (isset($chapter2)){
//says if variable chapter defined above is equal to variable chapter 2 which is defined below do something. This is not true the first time but it is the rest of the loop, even is is a million.
            if ($chapter == $chapter2) {
//variable chaptertd (which is called below) will equal to nothing if chapter equals to chapter2, this will happen at every exam (every ex tag in my xml file which is in the question above)
//this will avoid having repeated chapter, ie: chapter1 - exam one, chapter1 - exam 2, chapter1 exam 3, ect. will make it chapter 1, exam 1, exam 2, exam 3, ect
                $chaptertd = "";
//if chapter does not equal to chapter2
                }else {
//here we increment variable _2chapters that was 1 above, now is two, this is necessary so it could display two chapters side by side and break right before the third chapter, this will happen later
                $_2chapters++;
                $chapter2 = $chapter; //THIS PART IS EDITED, BUT NECESSARY
//Now we give a value to variable chaptertd, it was nothing before because I didn't want to repeat the title every time the loop found a new tag ex from my xml. This will only happen once in every chapter
                $chaptertd = "
        </td>
        <td align='"center'" valign='"top'">$chapter2";//here we create the html that variable chaptertd will be displaying after a new name from the attribute chapter is found. This will display the name of the chapter to our table
                }
//this else will only happen the first time the loop runs since only the first time is when the variable chapter2 is not defined, after this runs the variable chapter2 will have been defined
            }else {
//chapter2 will be the same as chapter, if chapter equals to the string chapter1 so will chapter2.
                $chapter2 = $chapter;
//here we create the same td as above since we want to display the name of the chapter the fist time it runs, if we don't do this the first chapter won't be display to the client
                $chaptertd = "
        <td align='"center'" valign='"top'">$chapter2";
            }
//This part you don't have to concern yourself with it, I made this because I needed it to display different info depending whether the user was allow to see that exam.
//the variable examval is defined outside this code, that's on my html code which would do nothing here since it uses javascript and css. this gets the attribute id from our ex tag.
    if ($examid < $studentexnum) {
        $exval = "lessthan";
    }elseif ($examid == 5) {
        $exval = "equalto";
    }elseif ($examid > 5) {
        $exval = "greaterthan";
    }
//here we say what happens when the variable _2chapters reaches the third attribute called chapter. we say if the remainder of variable _2chapters divided by 3 equals 0 do something
//else do nothing since we didn't define the else because we didn't needed it. this part will only happen at every third chapter, it will break from the previous chapter thus making
//it a new row right under the values of the tag ex which is under chapter 1 the third time the loops runs, but this will happen infinite amounts of time, after that it will be under
//chapter 3 and after that chapter 5 and so on.
            if ($_2chapters % 3 == 0) {
//here we reset the count back to one because if we don't and there's more than one tag ex under chapter 3, it will be braking after every ex
                $_2chapters = 1;
//here we echo the break from the previous chapter
            echo "
        </td>
    </tr>
    <tr id='"center'">";
    }
//here we echo the variable chaptertd which we gave different values to above depending whether the chapter's name has been declared already or not. If it has been declared, chaptertd
//won't show anything, if the chapter has never been declared it will create a new td and display the chapter's name and after that it will become nothing again
echo "$chaptertd<br />
            <a href='"#'" class='"modalInput'" rel='"#$exval'">$examname</a>";//here we show the client what's the name of the exams under the given chapter, there could be one or one hundred of this and it will only display the chapter once and will display the rest
//of the exam names one after the other
//here we say that chapter2 equals to chapter, this way chapter2 will equal to the name of that loop, if the next time it repeats there's a new chapter the value of chapter will change
//thus making this statement false above and that will force it to create a new td with the new name until another name appears.
            $chapter2 = $chapter;
}
//close the table to have a well formatted html file to display to the client.
echo "
        </td>
    </tr>
</table>";
?>

我其实在一段时间前就明白了，但是这个"智能论坛"不允许我在8小时前回答我自己的问题，因为我没有足够的积分之类的。这就好像是在说，因为我是新来的，所以我很笨，不能在8小时内自己找到解决问题的方法。所以我就去睡觉了。我只是想帮助那些将来可能会看到这篇文章的人，希望这个答案能回答他们的一些问题。

你的意思可能是…

foreach($exams as $exam)

…要从数组中获取一个项，而不是…

foreach($exams as $exams)