PHP验证和Javascript验证不能一起使用

当我将php表单验证代码与javascript验证代码结合使用时，当我按下“提交”按钮时，javascript代码无法正常工作。它将只验证第一个表单字段，而不验证其他三个字段，然后php将验证所有字段。在JavaScript完成表单验证之前，我不希望php表单验证执行任何操作。

当我仅使用php或仅使用javascript进行验证时，代码即可正常工作。我在这里想念什么？与表格开头有关吗？

"form name="contactform" id="contactform" method="post" 
action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" 
onsubmit="return validateentry();">"

我应该在“操作”转到另一个网页时进行php表单验证吗？

javascript代码：

function validateemail()
{
var emailentry=document.forms.contactform.email.value;
at=emailentry.indexOf("@");
period=emailentry.lastIndexOf(".");
if(at < 1 || ( period - at < 2 )) 
{
   alert("Please enter correct email in the format of '[email protected]'")
   document.forms.contactform.email.focus();
   return false;
}
return(true);
}


function validatephonenumber()
{
var re = /(?:\d{3}|\(\d{3}\))([-\/\.])\d{3}\1\d{4}/;  
    var numbers = document.forms.contactform.phone.value; 
    var verified = re.exec(numbers);  
    if (!verified)  
    {
alert("Please enter a phone number in the format of 999-999-9999");
return false;
}  
    return(true); 
}

function validateentry()
{
if(document.forms.contactform.name.value=="")
{
 alert("Please provide your name.");
 document.forms.contactform.name.focus();
 return false;
}

if(document.forms.contactform.company.value=="")
{
 alert("Please provide your company name. If you don't have one, simply state 
 that you don't.");
 document.forms.contactform.company.focus();
 return false;
}

 if(document.forms.contactform.email.value == "")
 {
 alert("Please provide an Email address.");
 document.forms.contactform.email.focus();
 return false;
 }else{
 var validformat=validateemail();
 if(validformat==false)
 {
 return false;
 }}

if(document.forms.contactform.phone.value=="")
{
 alert("Please provide a phone number in the format 999-999-9999.");
 document.forms.contactform.phone.focus();
 return false;
}
else if(document.forms.contactform.phone.value.length < 12)
{
    alert("Please provide the phone number in the format of 999-999-9999.");
    document.forms.contactform.phone.focus();
        return false;
}
    else
    {
    var validnumber=validatephonenumber();
    if(validnumber==false)
    {
    return false;
    }}

if(document.forms.contactform.msg.value=="")
{
 alert("Please provide a message.");
 document.forms.contactform.msg.focus();
 return false; 
}
 return(true);
}