How to call javascript function in php code?

Question

on my login form, i am putting server side validations and if error occurs i want to display those error just below the validated control. Now for this, i am trying to call javascript function to show validation message in php code but not able to call.

<?php

if($_SERVER['REQUEST_METHOD'] == 'POST')
{
if($_POST['txtUsername']=='')
{
    //here i want to call javascript function to display message    
}
}
?>
 <form action="login.php" method="POST">

 Username <input type="text" size="30" name="txtUsername" id="user" /><br />

 Password <input type="password" size="30" name="txtPassword" id="pass" /><br />

 <input type="submit" value="Login" name="loginSubmit"/>

</form>


<script type="text/javascript">

   function showMessage(value)
   {
    document.getElementById(value).innerHTML= value+"can not be empty."; 
   }
   </script>

Please tell me how to display server side validation just below the validated control in form.

Why don't you validate the inputs from form and then submit the form? — Sudip
– Sudip, Commented Feb 20, 2013 at 10:11
Would it not be useful to actually assign a jQeury script to the submit? The script should then be able to do the validation for you unless I am missing something — Bas Jansen
– Bas Jansen, Commented Feb 20, 2013 at 10:11
Its not working because You are using function before declaring it.Declare script first and then use php. — AZT
– AZT, Commented Oct 27, 2014 at 20:15

Yogesh Suthar · Accepted Answer · 2013-02-20 10:13:08Z

3

use this

if($_POST['txtUsername']=='')
{
     echo '<script> showMessage("txtUsername"); </script>';
}

answered Feb 20, 2013 at 10:13

Yogesh Suthar

30.5k18 gold badges75 silver badges100 bronze badges

@yogesh what if I need to pass the POST value in the function and then use in javascript to assign that value to input

Nehal
– Nehal

01/09/2016 13:03:41
Commented Jan 9, 2016 at 13:03

Add a comment |

Aamir Mahmood · Accepted Answer · 2013-02-20 10:25:04Z

3

Something like this

<html>
<head>
<script type="text/javascript">

   function showMessage(value)
   {
       document.getElementById(value).innerHTML= value+"can not be empty."; 
   }
   </script>
</head>
<body>
<?php

if($_SERVER['REQUEST_METHOD'] == 'POST')
{
    if($_POST['txtUsername']=='')
    {
        echo '<script> showMessage("txtUsername"); </script>';
    }
}
?>
 <form action="login.php" method="POST">

 Username <input type="text" size="30" name="txtUsername" id="txtUsername" /><br />

 Password <input type="password" size="30" name="txtPassword" id="txtPassword" /><br />

 <input type="submit" value="Login" name="loginSubmit"/>

</form>

</body>
</html>

edited Feb 20, 2013 at 10:25

answered Feb 20, 2013 at 10:10

Aamir Mahmood

2,7243 gold badges27 silver badges47 bronze badges

:: but i dont want to show message in alert box. i want to show as innerHTML

Kalpana Dixit
– Kalpana Dixit

02/20/2013 10:11:05
Commented Feb 20, 2013 at 10:11
check updated answer, also note that i have changed the IDs of the textboxes

Aamir Mahmood
– Aamir Mahmood

02/20/2013 10:11:42
Commented Feb 20, 2013 at 10:11
i just have added <script> tags around that please check now

Aamir Mahmood
– Aamir Mahmood

02/20/2013 10:17:30
Commented Feb 20, 2013 at 10:17
You need to define showMessage function above the code. check updated answer

Aamir Mahmood
– Aamir Mahmood

02/20/2013 10:24:02
Commented Feb 20, 2013 at 10:24

Add a comment |

Riste · Accepted Answer · 2013-09-06 12:10:57Z

You can put your php code anywhere you like let's say in the body like attribute. You can try the following code:

<body  <?php

        if($_SERVER['REQUEST_METHOD'] == 'POST')
{
if($_POST['txtUsername']=='')
{
  echo "onload = 'showMessage("VALUE")'";    
}
}
?> > // end of body start tag

 <form action="login.php" method="POST">

 Username <input type="text" size="30" name="txtUsername" id="user" /><br />

 Password <input type="password" size="30" name="txtPassword" id="pass" /><br />

 <input type="submit" value="Login" name="loginSubmit"/>

</form>
</body>

<script type="text/javascript">

   function showMessage(value)
   {
    document.getElementById(value).innerHTML= value+"can not be empty."; 
   }
   </script>

If the validation is successful the php code wont echo anything and the javascript function will not be called. Works for me :). Tell me if this helps.

Kanwaljit Singh · Accepted Answer · 2014-03-11 07:15:11Z

1

    <?php

    if($_SERVER['REQUEST_METHOD'] == 'POST')
    {
      if($_POST['txtUsername']=='')
      {
      ?>
          <script>
             //Define the function somewhere in the top or in external js and include it.
            callyourfunction();
          </script>
      <?php
      }
    }
?>              //Its not working

edited Mar 11, 2014 at 7:15

Kanwaljit Singh

4,3872 gold badges20 silver badges22 bronze badges

answered Feb 20, 2013 at 10:13

Samy

6324 silver badges14 bronze badges

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