通过PHP为搜索创建索引

我在为问题制作多维数组时遇到了一些问题.

我的第一个unsuccessful attempt如下.

#1

$result = pg_query_params ( $dbconn,"SELECT question_id,body
    FROM questions",array () 
);

while ( $row = pg_fetch_array ( $result ) ) {
    $question_body [ $row['question_id'] ] ['body'] = $row['body'];
    $question_index = explode ( " ",$question_body[ $row['question_id'] ] ['body'] ); 
    $question_index = array_unique ( $question_index ); 
}                                                                                                   
var_dump( $question_index );

这段代码的问题在于它结合了每个问题中的单词.
似乎我不能使用爆炸,因为它似乎只制作一个单维数组.

我还运行以下代码试图获取question_id unsuccessfully.

#2

while ( $row = pg_fetch_array ( $result ) ) {
    $question_body [ $row['question_id'] ] ['body'] = $row['body'];
    $question_index[ $row['question_id'] ] = explode ( " ",$question_body[ $row['question_id'] ] ['body'] );
    $question_index[ $row['question_id'] ]= array_unique ( $question_index );
}
var_dump( $question_index );