Validate empty field with php

Question

I need to validate an empty field with php and javascript, but both of the methods fail.

<form method="POST" name="contact_form"
action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>">
<input type="text" name="pickupaddress"  value="<?
 if($pickupaddress == ''){ 
echo "";} 
else{echo htmlentities($pickupaddress);}?> " id="pickupaddress"/>
<input type ="submit" name="submit" value"Reserve"/> 
</form>

//////// Php validation DOES NOT WORK////////

$pickupaddress ='';
$err ='';

$pickupaddress = $_POST['pickupaddress'];

if($pickupaddress == ''){   //if empty field, I also tried == ""
$err.="Please provide pick up address.";
}

///// Javascript validation does not work.


if(form.pickupaddress ==""){
alert("empty address!");
}

//when I click submit nothing happens. //I am thinking the problem is with

htmlentities($pickupaddress);

//Thanks for your help.

you have a white space in the value of your pickupaddress field value. .. so since ' ' != '' your validators never work. — David Chan
– David Chan, Commented Aug 13, 2012 at 22:40

Stano · Accepted Answer · 2012-08-13 22:59:52Z

1

Here is hopefully simpler answer:

$pickupaddress = trim($_POST['pickupaddress']); //trims the string
    if (empty($pickupaddress)){   //if empty field
    $err.="Please provide pick up address.";
}

answered Aug 13, 2012 at 22:59

Stano

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Comments

jaimerump · Accepted Answer · 2012-08-13 22:30:14Z

1

On the php side you can try trimming the value and then using empty() on the next line, though that will also invalidate 0, false, null, and other such values. Or you can try using isset.

For the javascript side you can try this function:

function IsEmpty(aTextField) {
    if ((aTextField.value.length==0) ||
       (aTextField.value==null)) {
        return true;
    }
    else { return false; }
}

found here: http://www.codetoad.com/javascript/isempty.asp

answered Aug 13, 2012 at 22:30

jaimerump

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Comments

JustBaron · Accepted Answer · 2017-10-04 12:24:50Z

1

$cid = $_POST['category'];

if (!empty($_POST['category']))
{
   echo "<script>alert('empty field');</script>";
}

edited Oct 4, 2017 at 12:24

JustBaron

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answered Oct 4, 2017 at 11:52

emilia chan

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1 Comment

mrun Over a year ago

Hi and welcome to SO! Although the code may speak for itself providing some details would help improve the quality of your answer!

wanovak · Accepted Answer · 2012-08-13 22:26:15Z

0

Where are you defining pickupaddress? Is it before the form or after? If the variable isn't defined, and depending on your server configuration, the value field of the input could be

Notice: undefined variable pickupaddress

Thus making the value != ''.

View your page source to ensure that the value is indeed empty.

answered Aug 13, 2012 at 22:26

wanovak

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Comments

r3bel · Accepted Answer · 2012-08-13 22:35:19Z

there was a spave " " in your string: echo htmlentities($pickupaddress);}?> " maybe that was the reason, because it was not an empty string but it was a space?

<form method="POST" name="contact_form"
action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>">

<input type="text" name="pickupaddress"  value="<?
if($pickupaddress != '') {
    echo htmlentities($pickupaddress);
}?>" id="pickupaddress"/>
<input type ="submit" name="submit" value"Reserve"/> 

</form>

and i guess you might want to have checked if the post value is set:

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

the php way works for me like that ;) (the message is displayed if i dont write anything)

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