当所选数据不存在于数据库中时，PHP未定义变量 [英] PHP undefined variable when selected data is not present in the database

问题描述

嗯，我的代码在数据库中存在的所选行时，它可以工作完美.但问题是当我选择一个根本不存在的数据时.它给了我一个错误，我的变量未定义.

这是脚本:

我正在显示输入类型文本..

<tr><td>目标</td></tr><tr><td><input ID="txtobjective" name="objective" value="<?php echo "" .$objective.""; ?>"type="text"/><br></td></tr>

我认为这是一个常见问题，我什至无法解决.我刚从使用 PHP 编码回来.有人可以建议我处理此类问题的好方法.提前致谢.

解决方案

将 $objective='' 放在代码之前.您的变量尚未设置.

Well, my code works when the selected row exists in the database, it works perfect. But the problem is when I am selecting a data that doesn't exist at all. It gives me an error that my variables are undefined.

This is the scripting:

<?php 
    include('Nethost.php');
        $patient = $_POST['patientid'];
        $diagnosisid = $_POST['diagnosis'];
        $pname = $_POST['patientname'];
        $d = $_POST['diagnosis'];
        $query = mysql_query("select objective from soapie WHERE patientid='$patient' AND subjective='$diagnosisid' LIMIT 1");

       while($rows = mysql_fetch_assoc($query))
        {
            if($rows==NULL) 
            {
                        echo "No data";         
            }
            else
            {
                        $objective = $rows['objective'];        
            }                       
    }
    ?>

I am displaying it input type text..

<table style="margin-left:auto; margin-right:auto">
    <tr>
    <td>Objective</td>
    </tr>
    <tr>
    <td><input ID="txtobjective" name="objective" value="<?php echo "" .$objective. ""; ?>" type="text" /><br></td>
    </tr>
    </table>

I think this is a common problem and I can't even solve it. I just got back from coding using PHP. Can someone suggest me a good practice to handle this kind of problems. Thanks in advance.

解决方案

Put $objective='' before code. Your variable has not been set.

<?php 
    include('Nethost.php');
        $patient = $_POST['patientid'];
        $diagnosisid = $_POST['diagnosis'];
        $pname = $_POST['patientname'];
        $d = $_POST['diagnosis'];
        **$objective='';**
        $query = mysql_query("select objective from soapie WHERE patientid='$patient' AND subjective='$diagnosisid' LIMIT 1");

       while($rows = mysql_fetch_assoc($query))
        {
            if($rows==NULL) 
            {
                        echo "No data";         
            }
            else
            {
                        $objective = $rows['objective'];        
            }                       
    }
    ?>

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