PHP，未捕获的TypeError：无法读取未定义的属性“ length”

Question

我正在尝试通过AJAX调用在PHP上创建可靠的下拉列表。 MySQL表上有9列。 我找到了示例代码。 有3个下拉列表。 我试图增加它们。

 <!doctype html public "-//w3c//dtd html 3.2//en"> <html> <head> <title></title> <META NAME="DESCRIPTION" CONTENT=""> <META NAME="KEYWORDS" CONTENT=""> <script type="text/javascript"> function ajaxFunction(choice) { { alert(choice.options.length);} var httpxml; try { // Firefox, Opera 8.0+, Safari httpxml=new XMLHttpRequest(); } catch (e) { // Internet Explorer try { httpxml=new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { httpxml=new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("Your browser does not support AJAX!"); return false; } } } function stateChanged() { if(httpxml.readyState==4) { //alert(httpxml.responseText); var myObject = JSON.parse(httpxml.responseText); for(j=document.myForm.state.options.length-1;j>=0;j--) { document.myForm.state.remove(j); } var state1=myObject.value.state1; var optn = document.createElement("OPTION"); optn.text = 'Select State'; optn.value = ''; document.myForm.state.options.add(optn); for (i=0;i<myObject.state.length;i++) { var optn = document.createElement("OPTION"); optn.text = myObject.state[i]; optn.value = myObject.state[i]; document.myForm.state.options.add(optn); if(optn.value==state1){ var k= i+1; document.myForm.state.options[k].selected=true; } } ////////////////////////// for(j=document.myForm.city.options.length-1;j>=0;j--) { document.myForm.city.remove(j); } var city1=myObject.value.city1; //alert(city1); for (i=0;i<myObject.city.length;i++) { var optn = document.createElement("OPTION"); optn.text = myObject.city[i]; optn.value = myObject.city[i]; document.myForm.city.options.add(optn); if(optn.value==city1){ document.myForm.city.options[i].selected=true; } } //////////////////// for(j=document.myForm.country.options.length-1;j>=0;j--) { document.myForm.country.remove(j); } var name1=myObject.value.name1; var optn = document.createElement("OPTION"); optn.text = 'Select Name'; optn.value = ''; document.myForm.country.options.add(optn); for (i=0;i<myObject.name.length;i++) { var optn = document.createElement("OPTION"); optn.text = myObject.name[i]; optn.value = myObject.name[i]; document.myForm.country.options.add(optn); if(optn.value==name1){ var k= i+1; document.myForm.name.options[k].selected=true; } } /////////////////////////// document.getElementById("txtHint").style.background='#00f040'; document.getElementById("txtHint").innerHTML='done'; //setTimeout("document.getElementById('txtHint').style.display='none'",3000) } } var url="ajax-dd3ck.php"; var country=myForm.country.value; if(choice != 's1'){ var state=myForm.state.value; var city=myForm.city.value; var name=myForm.name.value; }else{ var state=''; var city=''; var name=''; } url=url+"?country="+country; url=url+"&state="+state; url=url+"&city="+city; url=url+"&name="+name; url=url+"&id="+Math.random(); myForm.st.value=state; //alert(url); document.getElementById("txtHint2").innerHTML=url; httpxml.onreadystatechange=stateChanged; httpxml.open("GET",url,true); httpxml.send(null); document.getElementById("txtHint").innerHTML="Please Wait...."; document.getElementById("txtHint").style.background='#f1f1f1'; } </script> </head> <body > </head> <body> <div id="txtHint" style="width : 100px;background-color: #cccc33;">Message area</div> <br><br> <form name="myForm" action='ajax-dd3-details.php' method='post'"> <input type=hidden name=st value=0> <table width=500> <tr><td > Select Country<br><select name="country" id="s1" onchange="ajaxFunction(this);"> <option value=''>Select One</option> <?Php //require "../include/z_db1.php"; require "config.php";// connection to database $sql="select distinct country from student5 "; foreach ($dbo->query($sql) as $row) { echo "<option value=$row[country]>$row[country]</option>"; } ?> </select> </td><td ><select name=state id="s2" onchange="ajaxFunction(this)";> <option value=''>Select One</option></select></td> <td ><select name=city id="s3" onchange="ajaxFunction(this);"> <option value=''>Select One</option></select></td> <td ><select name=sex id="s4" onchange="ajaxFunction(this);"> <option value=''>Select One</option></select></td> </tr></tr> <tr><td colspan=3><input type=submit value='Submit'></td></tr> </form> </table> <br><br> <div id="txtHint2"></div> </body> </html> 

我编辑了这个php文件并添加了以下代码。 因为我想将名称列从mysql添加到下拉列表中：

 //////////////////// for(j=document.myForm.name.options.length-1;j>=0;j--) { document.myForm.name.remove(j); } var name1=myObject.value.name1; var optn = document.createElement("OPTION"); optn.text = 'Select Name'; optn.value = ''; document.myForm.name.options.add(optn); for (i=0;i<myObject.name.length;i++) { var optn = document.createElement("OPTION"); optn.text = myObject.name[i]; optn.value = myObject.name[i]; document.myForm.name.options.add(optn); if(optn.value==name1){ var k= i+1; document.myForm.name.options[k].selected=true; } } 

我还编辑了另一个php文件：

 <?Php require "config.php"; // connection details error_reporting(0);// With this no error reporting will be there ////////// ///////////////////////////////////////////////////////////////////////////// $country=$_GET['country'];// //$country='IND'; // To check you can use this $state1=$_GET['state']; $city1=$_GET['city']; $name1=$_GET['name']; //$state1="Andhra Pradesh"; ///////////// Validate the inputs //////////// // Checking country variable /// if((strlen($country)) > 0 and (!ctype_alpha($country))){ echo "Data Error"; exit; } // Checking state variable (with space ) /// if ((strlen($state1)) > 0 and ctype_alpha(str_replace(' ', '', $state1)) === false) { echo "Data Error"; exit; } // Checking class variable /// if((strlen($name1)) > 0 and (!ctype_alpha($name1))){ echo "Data Error"; exit; } /////////// end of input validation ////// if(strlen($country) > 0){ $q_country="select distinct(state) from student5 where country = '$country'"; }else{ $q_country="select distinct(state) from student5"; } //echo $q_country; $sth = $dbo->prepare($q_country); $sth->execute(); $state = $sth->fetchAll(PDO::FETCH_COLUMN); $q_state="select distinct(city) from student5 where "; if(strlen($country) > 0){ $q_state= $q_state . " country = '$country' "; } if(strlen($state1) > 0){$q_state= $q_state . " and state='$state1'";} $sth = $dbo->prepare($q_state); $sth->execute(); $city = $sth->fetchAll(PDO::FETCH_COLUMN); $q_name="select distinct(name) from student5 where "; if(strlen($country) > 0){ $q_state= $q_state . " country = '$country' "; } if(strlen($state1) > 0){$q_state= $q_state . " and state='$state1'";} if(strlen($city1) > 0){$q_city= $q_city . " and city='$city1'";} $sth = $dbo->prepare($q_city); $sth->execute(); $name = $sth->fetchAll(PDO::FETCH_COLUMN); $main = array('state'=>$state,'city'=>$city,'name'=>$name1, 'value'=>array("state1"=>"$state1","city1"=>"$city1", "name"=>"$name1")); echo json_encode($main); ////////////End of script ///////////////////////////////////////////////////////////////////////////////// ?> 

我在上面添加了该代码：

 $q_name="select distinct(name) from student5 where "; if(strlen($country) > 0){ $q_state= $q_state . " country = '$country' "; } if(strlen($state1) > 0){$q_state= $q_state . " and state='$state1'";} if(strlen($city1) > 0){$q_city= $q_city . " and city='$city1'";} $sth = $dbo->prepare($q_city); $sth->execute(); $name = $sth->fetchAll(PDO::FETCH_COLUMN); 

当我通过LAMP打开它时，新的下拉列表不起作用。 而且我得到了这个错误 。 我该如何解决？

编辑： 这就是我所说的“名称”

Answer 1

document.myForm.name.options.length这给你错误。 您必须使用select的name来获得options length 。 所以使用像document.myForm.country.options.length

因此，在您的方案中，您必须这样做。

在HTML中

<select name=country id='s1' onchange=ajaxFunction(this);>

而在JS中

function ajaxFunction(choice) {
    alert(choice.options.length);}

Answer 2

我可以看到一些小错误，这也无济于事！

<form name="myForm" action='ajax-dd3-details.php' method='post' ">
<input type=hidden name=st value=0>

表单开始标记的末尾有一个虚假的双引号，应简单地为：

<form name="myForm" action='ajax-dd3-details.php' method='post'>

而且您真的应该在字段中用引号将值括起来...

<input type='hidden' name='st' value='0' />

同样，您表单中的其他各种元素也是如此，例如：

<select name=country id='s1' onchange=ajaxFunction('s1');>

应该

<select name='country' id='s1' onchange="ajaxFunction('s1')">

我知道其他人可能会不同意，尤其是当HTML5对这种类型的事情看起来更放松时，采用和减少问题的出处是一种很好的做法。