PHP - How can a load page do some of the php - php

Question

I wish every time I reload or refresh the page. The disabled textbox still disabled. Because my purpose is to modify the textbox once time and then it will be disabled forever. Is this possible?
Below is my code
<tr>
<td><?php echo $lang_txt['leader_id'][$lang]; ?></td>
<td>:</td>
<td><?php if($_POST['txtLeaderID'] == ""){?><input type="text" name="txtLeaderID" id="txtLeaderID" style="width:400px;" value="<?php echo $merchant['LeaderID']; ?>" maxlength="20" /><?php }
else
{
?>
<input type="text" disabled="disabled" name="txtLeaderID" id="txtLeaderID" style="width:400px;" value="<?php echo $merchant['LeaderID']; ?>" maxlength="20" /><?php
}
?>
</td>
</tr>

Answer 1

Your variant will be worked with
if(!$_POST['txtLeaderID']){echo('<input type="text" name="txtLeaderID" id="txtLeaderID" style="width:400px;" value="'.$merchant['LeaderID'].'" maxlength="20" />')} else {echo('<input type="text" disabled="disabled" name="txtLeaderID" id="txtLeaderID" style="width:400px;" value="'.$merchant['LeaderID'].'" maxlength="20" />')}
For example:
<?php
if (!$_POST['username']){
echo('
<form action="'.$_SERVER['REQUEST_URI'].'" method="post">
Name: <input type="text" name="username" /><br />
Email : <input type="text" name="email" /><br />
<input type="submit" name="submit" value="Send POST!" />
</form>
');}
else{
echo('
<form>
Name: <input type="text" name="username" disabled="disabled"/><br />
Email : <input type="text" name="email" disabled="disabled"/><br />
</form>
');}
?>
But it didn't work, if we open it in a new tab. You must save this propery anywhere (session, cookie, sql)and check the stored values. it will be work in a new tab.
For example with session:
<?php
session_start();
if (!isset($_SESSION['data'])) {
$_SESSION['data'] = true;
echo('
<form action="'.$_SERVER['REQUEST_URI'].'" method="post">
Name: <input type="text" name="username" /><br />
Email : <input type="text" name="email" /><br />
<input type="submit" name="submit" value="Send POST!" />
</form>
');}
else{
echo('
<form>
Name: <input type="text" name="username" disabled="disabled"/><br />
Email : <input type="text" name="email" disabled="disabled"/><br />
</form>
');}
?>