Question

我正在尝试使用for循环检索前4个条目，但它似乎重复了1次4次。

这是我的代码：

$con=mysqli_connect("localhost","root","root","test");
// Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$result = mysqli_query($con,"SELECT * FROM activiteiten");
while($row = mysqli_fetch_array($result)) {
  for ($result = 1; $result <= 4; $result++) {
    echo "<div class='agenda_item' style='background-color:#F39'>";
    echo "<img src='images/soosavond_small.jpg'  class='soospict_small' />";
    echo "<div class='agenda_content'>";
    echo "<p class='datum'>" . $row['datum'] . "</p>";
    echo "<p class='onderwerp'>" . $row['naam_activiteit'] . "</p>";
    echo "<p class='details'>" . $row['beschrijving'] . "</p>";
    echo "</div>";
    echo "<a href='#'' class='pijlklein'>MEER INFO</a>";
    echo "</div>";
  }
}
mysqli_close($con);

Answer 1

您不需要 for 循环。我修改了代码，只检索前4项。查看cahnged查询 LIMIT 4 。

<?php
        $con=mysqli_connect("localhost","root","root","test");
        // Check connection
        if (mysqli_connect_errno()) {
          echo "Failed to connect to MySQL: " . mysqli_connect_error();
        }

        $result = mysqli_query($con,"SELECT * FROM activiteiten LIMIT 4");
        while($row = mysqli_fetch_array($result)) {
          echo "<div class='agenda_item' style='background-color:#F39'>";
          echo "<img src='images/soosavond_small.jpg'  class='soospict_small' />";
          echo "<div class='agenda_content'>";
          echo "<p class='datum'>" . $row['datum'] . "</p>";
          echo "<p class='onderwerp'>" . $row['naam_activiteit'] . "</p>";
          echo "<p class='details'>" . $row['beschrijving'] . "</p>";
          echo "</div>";
          echo "<a href='#'' class='pijlklein'>MEER INFO</a>";
          echo "</div>";
      }
        mysqli_close($con);
        ?>

Answer 2

你在while循环中有一个for循环。您可以删除for循环并使用MySQL中的LIMIT（如果只需要前4个条目，则可以通过PHP获取所有条目（性能更佳）更好）：

SELECT * FROM activiteiten LIMIT 4

如果您仍想使用php：

$results = 0;
while($row = mysqli_fetch_array($result) && $results < 4) {
    echo "<div class='agenda_item' style='background-color:#F39'>";
    ...
    $results++;
}

Answer 3

您呈现的代码 - 以与您看到的方式相同的方式混合。不需要for循环。您应该在MySQL查询中设置LIMIT，如下所示：

$con=mysqli_connect("localhost","root","root","test");
// Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$result = mysqli_query($con,"SELECT * FROM activiteiten LIMIT 0,4");
while($row = mysqli_fetch_array($result)) {
  echo "<div class='agenda_item' style='background-color:#F39'>";
  echo "<img src='images/soosavond_small.jpg'  class='soospict_small' />";
  echo "<div class='agenda_content'>";
  echo "<p class='datum'>" . $row['datum'] . "</p>";
  echo "<p class='onderwerp'>" . $row['naam_activiteit'] . "</p>";
  echo "<p class='details'>" . $row['beschrijving'] . "</p>";
  echo "</div>";
  echo "<a href='#'' class='pijlklein'>MEER INFO</a>";
  echo "</div>";
}
mysqli_close($con);

原始代码的问题是for与while的混合最终会出现在您展示的场景中，如while的PHP手册条目中所述：

while语句的含义很简单。它告诉PHP执行重复的嵌套语句，只要while表达式评估为TRUE。

所以你有while迭代结果，但是你也有for循环嵌套在那里。 100％不必要。

我调整它的方法是删除for循环，但也将LIMIT 0,4添加到MySQL查询中。这基本上告诉MySQL从第一行开始获取4行，称为0。

for循环检索相同的mysql行

3 个答案: