isset（$ _ POST ['tag-name']）已设置，但$ _POST ['tag-name']在选择动态列表时返回空

时间：2016-11-15 08:07:18

标签： php

我在php中创建了动态列表。

<select name="student" >
    <option selected disable class="hideoption">Student Name</option>
   <?php
     while ($row = mysqli_fetch_array($result, MYSQLI_BOTH)){
        echo<option value='".$row['path']."'>'".$row['studentName']."'</option>";
     }
  ?>   
</select>

当我选择列表时，它会给出空字符串。但是当我没有被选中时，它会返回第一个值Student Name。我试图从这一行获得价值。

if(isset($_POST['student'])){ 
   $selectedName = $_POST['student'];
}

我还尝试检查isset是设置还是空。 isset已设置但为空。 这是Google提供的唯一解决方案。想法？

修改

我已经解决了这个问题。以下答案的解释。

4 个答案:

答案 0 :(得分：1)

起初我认为$_POST['student']会在<option>标记内返回文字而我错了。我知道它返回应该在<option>属性中设置的值，所以我只是将值设置为$row['studentName']，因为$row['path']返回空字符串。如果我说错了，请纠正我。所以基本上，代码如下所示。

<select name="student" >
  <option selected disable class="hideoption">Student Name</option>
  <?php
     while ($row = mysqli_fetch_array($result, MYSQLI_BOTH)){
        echo<option value='".$row['studentName']."'>'".$row['studentName']."'</option>";
     }
 ?>   
</select>

感谢您的所有回复。你的回答让我想到我应该怎么做。

答案 1 :(得分：0)

使用以下代码：

<select name="student" id="student" >
    <option selected disable class="hideoption">Student Name</option>
   <?php
     while ($row = mysqli_fetch_array($result, MYSQLI_BOTH)){
        echo "<option name='".$row['studentName']."' value='".$row['path']."'>'".$row['studentName']."'</option>";
   }?>   
</select>

答案 2 :(得分：0)

您应该对选定的AElements @Name='3'

使用此行<fo:root> <fo:block>STEP 1 0000</fo:block> <fo:table> <fo:table-row> <fo:table-cell> <fo:block> 1000 </fo:block> </fo:table-cell> </fo:table-row> <fo:table-row> <fo:table-cell> <fo:block> 2000 </fo:block> </fo:table-cell> </fo:table-row> <fo:table-row> <fo:table-cell> <fo:block> 3000 </fo:block> </fo:table-cell> </fo:table-row> </fo:table> <fo:block>STEP 2 1000</fo:block> <fo:table> <fo:table-row> <fo:table-cell> <fo:block> 0100 </fo:block> </fo:table-cell> </fo:table-row> <fo:table-row> <fo:table-cell> <fo:block> 0300 </fo:block> </fo:table-cell> </fo:table-row> </fo:table> <fo:block>STEP 2 2000</fo:block> <fo:table> <fo:table-row> <fo:table-cell> <fo:block> 0500 </fo:block> </fo:table-cell> </fo:table-row> </fo:table> <fo:block>STEP 2 4000</fo:block> <fo:table> <fo:table-row> <fo:table-cell> <fo:block> 0600 </fo:block> </fo:table-cell> </fo:table-row> </fo:table> <fo:block>STEP 3 0600</fo:block> <fo:table> <fo:table-row> <fo:table-cell> <fo:block> 0010 </fo:block> </fo:table-cell> </fo:table-row> </fo:table> </fo:root> 
<xsl:transform version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:fo="http://www.w3.org/1999/XSL/Format" 
>
    <xsl:output indent="yes" />



    <!-- all <AElement> we consider for output, indexed by their @Name and group ID -->
    <xsl:key name="AElementGroup1" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '1'][1]))
    " />
    <xsl:key name="AElementGroup2" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '2'][1]))
    " />
    <xsl:key name="AElementGroup3" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '3'][1]))
    " />
    <xsl:key name="AElementGroup4" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '4'][1]))
    " />
    <xsl:key name="AElementGroup5" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '5'][1]))
    " />
    <xsl:key name="AElementGroup6" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '6'][1]))
    " />
    <xsl:key name="AElementGroup7" match="AElement[AElement/Child1 = 'E']" use="
        concat(@Name, '|', generate-id(preceding-sibling::AElement[@Name = '7'][1]))
    " />

    <xsl:template match="/">
        <fo:root>
        <fo:layout-master-set>
        <fo:simple-page-master
        master-name="DIN-A4-Landscape"
        page-height="210mm"
        page-width="297mm"
        margin-left="1mm"
        margin-right="1mm"
        margin-top="1mm"
        margin-bottom="1mm"
            >
          <fo:region-body margin="1mm"/>
          <fo:region-before region-name="header" extent="5mm"/>
          <fo:region-after region-name="footer" extent="15mm"/>
          <fo:region-start  region-name="left"   extent="5mm"/>
          <fo:region-end    region-name="right"  extent="5mm"/>
        </fo:simple-page-master>
      </fo:layout-master-set>
      <fo:page-sequence master-reference="DIN-A4-Landscape">
        <fo:flow flow-name="xsl-region-body">                      
            <xsl:call-template name="ink">
                <xsl:with-param name="Now" select="1"/>
            </xsl:call-template>
        </fo:flow>
      </fo:page-sequence>

        </fo:root>
    </xsl:template>

    <xsl:template name="ink">

    <xsl:param name="Now"/>
    <xsl:param name="Next" select="$Now + 1"/>
    <xsl:param name="Ende" select="3"/>

    <xsl:apply-templates select="ROOT">
      <xsl:with-param name="nowStep" select="$Now"/>
      <xsl:with-param name="nextStep" select="$Next"/>
    </xsl:call-template>

    <xsl:if test="$Ende > $Now">

      <xsl:call-template name="ink">
        <xsl:with-param name="Now" select="$Now + 1"/>     
    </xsl:call-template>
    </xsl:if>

  </xsl:template>

    <xsl:template match="ROOT">
        <xsl:param name="nowStep"/>
        <xsl:param name="nextStep"/>

        <xsl:for-each select="AElement[@Name = $nowStep]">
            <xsl:variable name="groupId" select="generate-id()" />            
                <xsl:variable name="groupKey" select="concat($nextStep, '|', $groupId)" />
                <fo:block><xsl:value-of select="concat('STEP ' , $nowStep)" /></fo:block>

<xsl:variable name="group">
    <xsl:value-of select="concat('InternalElementGroup',$nowStep)"/>
</xsl:variable>

<xsl:if test="count(key($group, $groupKey))>=1">

                <fo:table page-break-after="always">
                    <fo:table-body>
                    <xsl:choose>
                    <xsl:when test="$nowStep = 1">
                        <xsl:apply-templates select="key('AElementGroup1', $groupKey)/AElement" />
                    </xsl:when>
                    <xsl:when test="$nowStep = 2">
                        <xsl:apply-templates select="key('AElementGroup2', $groupKey)/AElement" />
                    </xsl:when>
                    <xsl:when test="$nowStep = 3">
                        <xsl:apply-templates select="key('AElementGroup3', $groupKey)/AElement" />
                    </xsl:when>
                    </xsl:choose>


                    </fo:table-body>
                </fo:table>
</xsl:if>            
        </xsl:for-each>
    </xsl:template>

    <xsl:template match="AElement/AElement">
        <fo:table-row>
            <fo:table-cell>
                <fo:block><xsl:value-of select="Child2"/></fo:block>
            </fo:table-cell>
        </fo:table-row>
    </xsl:template>

</xsl:transform>

答案 3 :(得分：0)

@dongcheng这是相同的代码，但具有更好的对齐方式。所以你可以清楚地看到你的代码。

<select name="student">
    <option selected disable class="hideoption">Student Name</option>
   <?php
     while($row = mysqli_fetch_array($result, MYSQLI_BOTH)) {
        echo '<option value="' . $row['path'] . '">' . $row['studentName'] . '</option>';
     }
   ?>   
</select>

使用

$selectedStudent = !empty($_POST['student']) ? $_POST['student'] : '';
if ($selectedStudent) {
  // your code
}
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