在PHP中嵌套if-else语句 - nesting if else statements in PHP

我正试图根据mySQL数据库查询的结果对php页面进行图形更改。

<?php
$find_howto=mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND `pagename`='_I1' ORDER BY `answer` DESC") or die("Error fetching course selection, How To Use The Course");
if(mysql_num_rows($find_howto)>=1)
{   
$howto_data=mysql_fetch_assoc($find_howto);
if($howto_data['answer'] == "yes")
{
$count="red";
}elseif($howto_data['answer'] == "visited")
{
$count="yellow";
}
$find_quiz=mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND `pagename`='_I2' ORDER BY `answer` DESC") or die("Error fetching course selection, Quick Quiz");
if(mysql_num_rows($find_quiz)>=1)
{   
$quiz_data=mysql_fetch_assoc($find_quiz);
if($quiz_data['answer'] == "yes")
{
$count="red";
}elseif($quiz_data['answer'] == "visited")
{
$count="yellow";
}
}
if($count == "red")
{
echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionRed.gif" width="250" height="18"></a></td>';
}elseif($count == "yellow")
{
echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionYellow.gif" width="250" height="18"></a></td>';
}else{
echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionGreen.gif" width="250" height="18"></a></td>';
}
?>

如果第一个查询的结果是"是"，那么我给了"count"变量值"red"。

如果第一个查询的结果是"visited"，那么我给了"count"变量值"yellow"。

逻辑可能是正确的，但编码错误。

如何使"if/elseif/else"在上面起作用？事实上，我有10个街区要处理，而不仅仅是两个。但如果这有效，我可以添加其余部分。

更新的解决方案：好的。我设法用不同的方式（在很多帮助下）：

<?php
$find_intro_comp=mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND (`pagename`='_I1' OR `pagename`='_I2' OR `pagename`='_I3' OR `pagename`='_I4' OR `pagename`='_I5' OR `pagename`='_I6' OR `pagename`='_I7' OR `pagename`='_I8' OR `pagename`='_I9' OR `pagename`='_I10') AND `answer`='yes'") or die("Error pulling intro completed");
if(mysql_num_rows($find_intro_comp)>=10) // the number 10 depends on how many pages there are.
{
    echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionRed.gif" width="250" height="18"></a></td>';
}else{
$find_intro_visit=mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND (`pagename`='_I1' OR `pagename`='_I2' OR `pagename`='_I3' OR `pagename`='_I4' OR `pagename`='_I5' OR `pagename`='_I6' OR `pagename`='_I7' OR `pagename`='_I8' OR `pagename`='_I9' OR `pagename`='_I10') AND `answer`='visited'") or die("Error pulling intro visited");
if(mysql_num_rows($find_intro_visit)>=1)
    {
        echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionYellow.gif" width="250" height="18"></a></td>';
    }else{
        echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionGreen.gif" width="250" height="18"></a></td>';
    }
}
?>

您终于错过了}。此外，请在代码中添加适当的选项卡序列，以便更好地使用任何IDE。

$find_howto = mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND `pagename`='_I1' ORDER BY `answer` DESC") or die("Error fetching course selection, How To Use The Course");
if (mysql_num_rows($find_howto) >= 1) {
    $howto_data = mysql_fetch_assoc($find_howto);
    if ($howto_data['answer'] == "yes") {
        $count = "red";
    } elseif ($howto_data['answer'] == "visited") {
        $count = "yellow";
    }
    $find_quiz = mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND `pagename`='_I2' ORDER BY `answer` DESC") or die("Error fetching course selection, Quick Quiz");
    if (mysql_num_rows($find_quiz) >= 1) {
        $quiz_data = mysql_fetch_assoc($find_quiz);
        if ($quiz_data['answer'] == "yes") {
            $count = "red";
        } elseif ($quiz_data['answer'] == "visited") {
            $count = "yellow";
        }
    }
    if ($count == "red") {
        echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionRed.gif" width="250" height="18"></a></td>';
    } elseif ($count == "yellow") {
        echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionYellow.gif" width="250" height="18"></a></td>';
    } else {
        echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionGreen.gif" width="250" height="18"></a></td>';
    }
}

您必须使用while循环从数据库中提取所有结果，然后您可以使用嵌套的if-else检查提取值

我建议您从SQL查询中删除AND页面名称='_I2'部分（使其代码更庞大，对SQL服务器的多次重复查询）

您还可以通过在SQL查询中指定PHP逻辑来跳过它（请参见：http://dev.mysql.com/doc/refman/5.0/en/case.html)

似乎有编号，所以按页面名称排序应该是正常的

您应该声明块上的计数，并且您错过了一个制动。。

  <?php
  $count;
$find_howto=mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND `pagename`='_I1' ORDER BY `answer` DESC") or die("Error fetching course selection, How To Use The Course");
if(mysql_num_rows($find_howto)>=1)
{   
$howto_data=mysql_fetch_assoc($find_howto);
if($howto_data['answer'] == "yes")
{
$count="red";
}elseif($howto_data['answer'] == "visited")
{
$count="yellow";
}
}//
$find_quiz=mysql_query("SELECT * FROM `answers` WHERE `username`='$username' AND `pagename`='_I2' ORDER BY `answer` DESC") or die("Error fetching course selection, Quick Quiz");
if(mysql_num_rows($find_quiz)>=1)
{   
$quiz_data=mysql_fetch_assoc($find_quiz);
if($quiz_data['answer'] == "yes")
{
$count="red";
}elseif($quiz_data['answer'] == "visited")
{
$count="yellow";
}
}
if($count == "red")
{
echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionRed.gif" width="250" height="18"></a></td>';
}elseif($count == "yellow")
{
echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionYellow.gif" width="250" height="18"></a></td>';
}else{
echo '<img name="Introduction" border="0" src="../img/directories/main/IntroductionGreen.gif" width="250" height="18"></a></td>';
}
?>