Iterating FOREACH arrays in a FOR loop

I've been trying to learn PHP for the past week and I'm stuck at a particular problem. Please excuse my poorly worded title as I haven't grasped the jargon yet.

Here's my code:

$query = "SELECT $tablefields FROM $tablename";
$sth = $dbconn->prepare($query);

for ($x = 1; $x <=3; $x++){
    echo '<br /> This is an iteration ',$x;

      $sth->execute();
      foreach ($sth->fetchall() as $row) 
      { 
      $results = $row[$tablefields];
      echo $results, '<br />'
      ; 
      }

}

I want the code to output as below:

This is iteration No. 1
Apple
Orange
Banana
Kiwi

This is iteration No. 2
Apple
Orange
Banana
Kiwi

This is iteration No. 3
Apple
Orange
Banana
Kiwi

Now, the above code does the job just fine but when I want to increase the iterations $x<=20, and the fruit options to 20 items, there's a noticeable slowdown in the page rendering. I was wondering whether it's because the code is querying the MySQL database 20 times? Is there a better way to structure the code so that it's more efficient?

---

Because you do MySQL query 20 times. You can cache the result and then loop using the cache. For example:

$query = "SELECT $tablefields FROM $tablename";
$sth = $dbconn->prepare($query);
$sth->execute();

$result = "";
foreach ($sth->fetchall() as $row) {
    $result .= $row[$tablefields] . "<br>";
}

for ($x = 1; $x <=3; $x++){
    echo '<br /> This is an iteration ' . $x;
    echo $result;
}

---

$x=1;
foreach ($sth->fetchall() as $row){ 
      echo '<br /> This is an iteration ',$x;
      $results = $row[$tablefields];
      echo $results; 
      $x++;
}

您可以使用上面的代码，而不是一起使用for循环和foreach。

---

Here is the thing..

I don't why you are executing query thrice or each time loop is running. But here is the little improvement over your code. Take a look.

$query = "SELECT $tablefields FROM $tablename";
$sth = $dbconn->prepare($query);
$sth->execute();
$data = "";
foreach ($sth->fetchall() as $row) {
   $data .= $row[$tablefields] . "<br>";
}

for ($x = 1; $x <=3; $x++){
   echo '<br /> This is an iteration ' . $x;
   echo $data;
}

链接地址: http://www.djcxy.com/p/59076.html

上一篇: PHP脚本不传递数组变量的URL

下一篇: 在FOR循环中迭代FOREACH数组