PHP：显示具有公共列约束的数组的值

Question

I have a multidimensional array like this:

Array ( 

[0] => Array ( [ans_id] => 1 [ans_name] => PHP Hypertext Preprocessor [ques_id] => 1 [right_ans] => Yes [ques_name] => What is the acronym of PHP? [section_id] => 1 [section_name] => PHP ) 

[1] => Array ( [ans_id] => 2 [ans_name] => Preety Home Page [ques_id] => 1 [right_ans] => No [ques_name] => What is the acronym of PHP? [section_id] => 1 [section_name] => PHP ) 

[2] => Array ( [ans_id] => 3 [ans_name] => Programmed Hypertext Page [ques_id] => 1 [right_ans] => No [ques_name] => What is the acronym of PHP? [section_id] => 1 [section_name] => PHP ) 

[3] => Array ( [ans_id] => 4 [ans_name] => Programmed Hypertext Preprocessor [ques_id] => 1 [right_ans] => No [ques_name] => What is the acronym of PHP? [section_id] => 1 [section_name] => PHP ) ) 

My table is like this:

ans_id  ans_name                       ques_id                right_ans

1   PHP Hypertext Preprocessor           1                         Yes

2   Preety Home Page                     1                          No

3   Programmed Hypertext Page            1                          No

4   Programmed Hypertext Preprocessor    1                          No

5   Andy Suraski                        12                          No

6   Zeev Gutman                         12                          No

7   Rasmus Lerdorf                      12                         Yes

8   Perl                                12                          No

I want to retrieve the answers in sets of common question id's

i.e. one set of all answers for Ques_id='1', 2nd set of all answers for ques_id='12', etc.

I am supposed to use this code:

foreach($all_ans_cat as $r)
{                       
   echo $r['ans_id']."  ".$r['ans_name']."<br>";
}

This is retrieving all the values present in the table as one set and again in the 2nd set the same values are being displayed.

Answer 1

Select all answers sorted by ques_id and generate array with structure needed

$questions = array();
$prevQuestionId = null;
foreach ($all_ans_cat as $r) {
    if ($r['ques_id'] !== $prevQuestionId) {
        $questions[] = array(); 
    }
    $questions[sizeof($questions)-1][] = $r;
    $prevQuestionId = $r['ques_id'];
}

Result array would be:

0:
    - [ans1, ques1]
    - [ans2, ques1]
    ...
1: 
    - [ans5, ques13]
    - [ans6, ques13]
    ...
...