Null textbox then Redirect - php

Question

So i have a form method post in index.php where in it will send the data from a textbox to another page which is print.php.
now what i want to do is if the textbox from index.php is null it wont redirect to print.php or if it redirect to print.php it will be redirected back to index.php.
index.php format
<form action="print.php" method="post" target="_blank">
<input type="text" name="faidf" id="faidf" size="25" value="" maxlength="25"/></td>
<input type ="submit" value="Print">
print.php
<?php
$faidf = $_POST['faidf'];
if(isset($_POST['faidf'])) {
echo "<td><font size=2>FAID:$faidf</td><td></font></td>";
}
else {
echo "FAID is missing";
}
?>
instead of FAID is missing could i redirect it home because i have about 10more php wherein it needs the variable of $faidf so the whole printd.php is utterly useless if the textbox is blank.thanks

Answer 1

You can do this by two ways:
Way 1:
Use JQuery/JavaScript for the form validation process onsubmit of the form. It will redirect only in case where there is data found in textbox.
Way 2:
Check the length of provided post data and if the length is less than 1 return it to the previous page.
I will advice you to use the JavaScript/JQuery as it will run on all cross browsers and easy to implementation and changed easyly

Answer 2

first add onchange function to your textbox
<input type="text" onchange="myFunction(this)" name="faidf" id="faidf" size="25" value="" maxlength="25"/>
and add an Id for the button
<input type ="submit" value="Print" id="btn" />
and add script tag in your page :
function myFunction(e)
{
var x=document.getElementById("btn");
if (e.value == ''){
x.setAttribute('disabled','disabled');
}else{
x.removeAttribute('disabled');
}
}
and instead of your echo at print.php add location header
header("Location: index.php");