<div>
Just stating a problem statement isn't quite useful, is it? Post some values, post the sql is being used / issued, share some data / error received, etc. 
 
All I can guess is you are not passing the date in correct format. Format used should be yyyy-MM-dd.
</div>

student

Souvik Misra

<div>
There is nothing wrong with 

<pre><code class="code-1 nolinks" id="code-20-42541959-1">$DOB = &quot;$DOB[2]-$DOB[0]-$DOB[1]&quot;;
</code></pre>
This is perfectly legal - the only change I would make is to put the array values in { } 

<pre><code class="code-1 nolinks" id="code-20-42541959-2">$DOB = &quot;{$DOB[2]}-{$DOB[0]}-{$DOB[1]}&quot;;
</code></pre>
This is arguably better than concatenation which makes for far messier code. 
 
If your date is in MM / DD / YYYY format then to convert it you can use the <a href="http://php.net/manual/en/function.date.php" rel="ugc">date()</a> and <a href="http://" rel="ugc nofollow">strtotime()</a> functions 

<pre><code class="code-1 nolinks" id="code-20-42541959-3">$DOB = date('Y-m-d', strtotime($inputDate));
</code></pre>
Where $inputDate is your MM/DD/YYYY value from your post. To use it in your code you can do this 

<pre><code class="code-10 nolinks" id="code-20-42541959-4">// FIRST NEVER ASSUME YOUR POST DATA IS VALID OR EXISTS
$inputDate = isset($_POST['DOB']) ? $_POST['DOB'] : false;

// ASSUMES THE OTHER FIELDS $password, $F_name ETC ARE RETRIEVED BEFORE QUERY

// IF DATE IS PRESENT THEN PROCEED
if ($inputDate) {
 $DOB = date('Y-m-d', strtotime($inputDate));
 $sql = &lt;&lt;&lt; QUERY
INSERT INTO signin (
 F_name,
 U_name,
 password,
 email,
 DOB,
 phn
)
VALUES (
 '{$F_name}',
 '{$U_name}',
 '{$password}',
 '{$email}',
 '{$DOB}',
 '{$phn}'
)
QUERY; 
}
</code></pre>
Note in the above I have used <a href="http://php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc" rel="ugc">HEREDOC</a> notation for the query - this makes formatting of large text blocks easier as it allows for double and single quotes as well as variable insertion. 
Note also the use of the { } around the variable names - these are optional, usually used to remove ambiguity from variables embedded in strings - but I use them by default. 
 
I would also consider using a prepared statement for the above. 
 
Let's look at your error though. Something does not make sense - you have obviously not posted all your code - as the error references line 20 which is not useful to us as you have posted only 4 lines of code. 
 
If the script was bugging out with this in the Query &quot;/2017-03-24/&quot; - then we would need to see what the RAW POST is coming in because that value does not look like it could have been created with the code you have. 
 
I am unable to repeat the result you are getting. 
 
Suggestion 
1. Post your full source 
2. On line 1 of your script (after the &lt;?php) put this code 

<pre><code class="code-1 nolinks" id="code-20-42541959-5">echo &quot;&lt;pre&gt;&quot; . print_r($_POST, true) . &quot;&lt;/pre&gt;&quot;;
</code></pre>
And post that output here.
</div>

<div>
Pretty sure the value of a Date field is always in the format of yyyy-mm-dd when it's POSTed. You're trying to explode that value on the slash - explode(&quot;/&quot;,$DOB). Because the value has no slashes, you will only ever end up with 1 entry in your DOB array: &nbsp;$DOB[0] = 'yyyy-mm-dd' 
 
That's the reason you're getting the Undefined Offset errors. $DOB[1] and $DOB[2] don't exist! 
 
Because the Date is passed in a standard way, you're better off using the built-in date functions: 
 
$dob = new DateTime($_POST['DOB']); 
$formattedDoB = $dob-&gt;format(&quot;y-m-d&quot;); // set your format here to whatever you need. 
 
Then insert the $formattedDoB into your Query.
</div>

<div>
Post the 
<pre><code class="code-1 nolinks" id="code-20-42541989-1">signin.php 
</code></pre>
and 
<pre><code class="code-1 nolinks" id="code-20-42541989-2">.sql
</code></pre>
 file. The information you posted is not enough to guarantee a solution.
</div>

<div>
here ,is the whole code 
 
 

<pre><code class="code-10 nolinks" id="code-20-42542108-1">&lt;?php
 $servername = &quot;localhost&quot;;
 $username = &quot;root&quot;;
 $password = &quot;&quot;;
 $dbname = &quot;blogdata&quot;;

 $conn = mysqli_connect($servername, $username, $password, $dbname);

 if (!$conn) {
 die(&quot;Connection failed: &quot; . mysqli_connect_error());
 }
	if($_POST){
	$F_name=$_POST['Full_name'];
	$U_name=$_POST['User_Name'];
	$password=$_POST['password'];
	$email=$_POST['e-mail'];
	$phn=$_POST['mobileno'];
	$DOB=$_POST['DOB'];
	$DOB = explode(&quot;/&quot;,$DOB);
	 $DOB = &quot;{$DOB[2]}-{$DOB[0]}-{$DOB[1]}&quot;;
	 	 $sql = &quot;INSERT INTO signin (F_name,U_name,password,email,DOB,phn)VALUES ('$F_name','$U_name','$password','$email','$DOB','$phn')&quot;;
	if (mysqli_query($conn, $sql)) {
	 echo &quot;New record created successfully&quot;;
	} else {
	 echo &quot;Error: &quot; . $sql . &quot;&lt;br&gt;&quot; . mysqli_error($conn);
	}
	mysqli_close($conn);
	}
?&gt;


&lt;html&gt;
&lt;body&gt;
&lt;head&gt;
&lt;/head&gt;
&lt;title&gt;Blogger's Arena&lt;/title&gt;
&lt;link href=&quot;themes/1/js-image-slider.css&quot; rel=&quot;stylesheet&quot; type=&quot;text/css&quot; /&gt;
 &lt;script src=&quot;themes/1/js-image-slider.js&quot; type=&quot;text/javascript&quot;&gt;&lt;/script&gt;
 &lt;link href=&quot;generic.css&quot; rel=&quot;stylesheet&quot; type=&quot;text/css&quot; /&gt;
&lt;/head&gt;
&lt;body style=&quot;background-image:url(images/Blurred-Background-Sunset-3c-Free.jpg)&quot;&gt;
&lt;h1 style=&quot;background-color:green;text-align:center;color:red;&quot;&gt;Welcome to Blogger's Arena&lt;/h1&gt;
 &lt;div id=&quot;sliderFrame&quot;&gt;
 &lt;div id=&quot;slider&quot;&gt;
		
 &lt;img src=&quot;images/blogging_image.jpg&quot;/&gt;
 &lt;/a&gt;
			
 &lt;img src=&quot;images/blog-793047_960_720.jpg&quot;/&gt;
 &lt;img src=&quot;images/download.jpg&quot;/&gt;
 &lt;img src=&quot;images/to-blog.jpg&quot;/&gt;
 &lt;img src=&quot;images/i-think.jpg&quot;/&gt;
 
	 &lt;/div&gt;
 &lt;div id=&quot;htmlcaption&quot; style=&quot;display: none;&quot;&gt;
 
 &lt;/div&gt;
 &lt;/div&gt;

 &lt;div class=&quot;div2&quot;&gt;
 
 &lt;/div&gt;
&lt;p style=&quot;color:LightCoral;text-align:center;font-size: 150%;font-family: &quot;Times New Roman&quot;, Times, serif;&quot;&quot;&gt;Write what you think.&lt;/p&gt;
&lt;p style=&quot;color:LightCoral;text-align:center;font-size: 150%;font-family: &quot;Times New Roman&quot;, Times, serif;&quot;&quot;&gt;Write to decorate your thoughts with words&lt;/p&gt;

&lt;form action=&quot;&quot; method=&quot;post&quot;&gt;
&lt;p align=&quot;center&quot;&gt;
Full Name:&lt;input type=&quot;text&quot; name=&quot;Full_name&quot;size=&quot;25&quot;maxlength=&quot;30&quot;&gt;&lt;br&gt;&lt;br&gt;
User Name:&lt;input type=&quot;text&quot; name=&quot;User_Name&quot;size=&quot;25&quot;maxlength=&quot;30&quot;&gt;&lt;br&gt;&lt;br&gt;
Password:&lt;input type=&quot;password&quot; name=&quot;password&quot;&gt;&lt;br&gt;&lt;br&gt;
Email id:&lt;input type=&quot;text&quot; name=&quot;e-mail&quot;size=&quot;30&quot;&gt;&lt;br&gt;&lt;br&gt;
DOB:&lt;input type=&quot;date&quot; name=&quot;DOB&quot;&gt;&lt;br&gt;&lt;br&gt;

Phone number:&lt;input type=&quot;text&quot; name=&quot;mobileno&quot;size=&quot;30&quot;&gt;&lt;br&gt;&lt;br&gt;
&lt;input type=&quot;submit&quot; value=&quot;Submit&quot;&gt;
&lt;input type=&quot;reset&quot; value=&quot;Clear All&quot;&gt;
&lt;/p&gt;
&lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>
</div>

<div>
Please submit the output to the following. Place this at the top of your script 

<pre><code class="code-1 nolinks" id="code-20-42542139-1">echo &quot;&lt;pre&gt;&quot; . print_r($_POST, true) . &quot;&lt;/pre&gt;&quot;;
</code></pre>
We need to see what is in the DOB post variable.
</div>

<div>
Just a comment: Your HTML contains errors, also does you inlined CSS... 
 
E.g. 

<pre><code class="code-10 nolinks" id="code-20-42542142-1">&lt;!DOCTYPE html&gt;
&lt;html lang=&quot;en&quot;&gt;

&lt;head&gt;
 &lt;title&gt;Blogger's Arena&lt;/title&gt;
 &lt;link href=&quot;generic.css&quot; rel=&quot;stylesheet&quot; type=&quot;text/css&quot; /&gt;
 &lt;link href=&quot;themes/1/js-image-slider.css&quot; rel=&quot;stylesheet&quot; type=&quot;text/css&quot; /&gt;
 &lt;script src=&quot;themes/1/js-image-slider.js&quot; type=&quot;text/javascript&quot;&gt;&lt;/script&gt;
 &lt;style&gt;
 body {
 background: url(images/Blurred-Background-Sunset-3c-Free.jpg);
 }

 h1 {
 background-color: green;
 text-align: center;
 color: red;
 }

 #htmlcaption {
 display: none;
 }

 #p1 {
 color: LightCoral;
 text-align: center;
 font-size: 150%;
 font-family: &quot;Times New Roman&quot;, Times, serif;
 }

 #p2 {
 color: LightCoral;
 text-align: center;
 font-size: 150%;
 font-family: &quot;Times New Roman&quot;, Times, serif;
 }

 #pform {
 text-align: center;
 vertical-align: middle;
 }
 &lt;/style&gt;
&lt;/head&gt;

&lt;body&gt;
 &lt;h1&gt;Welcome to Blogger's Arena&lt;/h1&gt;
 &lt;div id=&quot;sliderFrame&quot;&gt;
 &lt;div id=&quot;slider&quot;&gt;
 &lt;img alt=&quot;(none)&quot; src=&quot;images/blogging_image.jpg&quot; /&gt;
 &lt;img alt=&quot;(none)&quot; src=&quot;images/blog-793047_960_720.jpg&quot; /&gt;
 &lt;img alt=&quot;(none)&quot; src=&quot;images/download.jpg&quot; /&gt;
 &lt;img alt=&quot;(none)&quot; src=&quot;images/to-blog.jpg&quot; /&gt;
 &lt;img alt=&quot;(none)&quot; src=&quot;images/i-think.jpg&quot; /&gt;
 &lt;/div&gt;
 &lt;div id=&quot;htmlcaption&quot;&gt; &lt;/div&gt;
 &lt;/div&gt;
 &lt;div class=&quot;div2&quot;&gt; &lt;/div&gt;
 &lt;p id=&quot;p1&quot;&gt;Write what you think.&lt;/p&gt;
 &lt;p id=&quot;p2&quot;&gt;Write to decorate your thoughts with words&lt;/p&gt;
 &lt;form action=&quot;submit&quot; method=&quot;post&quot;&gt;
 &lt;p id=&quot;pform&quot;&gt;
 Full Name:
 &lt;input type=&quot;text&quot; name=&quot;Full_name&quot; size=&quot;25&quot; maxlength=&quot;30&quot;&gt;
 &lt;br&gt;
 &lt;br&gt; User Name:
 &lt;input type=&quot;text&quot; name=&quot;User_Name&quot; size=&quot;25&quot; maxlength=&quot;30&quot;&gt;
 &lt;br&gt;
 &lt;br&gt; Password:
 &lt;input type=&quot;password&quot; name=&quot;password&quot;&gt;
 &lt;br&gt;
 &lt;br&gt; Email id:
 &lt;input type=&quot;text&quot; name=&quot;e-mail&quot; size=&quot;30&quot;&gt;
 &lt;br&gt;
 &lt;br&gt; DOB:
 &lt;input type=&quot;date&quot; name=&quot;DOB&quot;&gt;
 &lt;br&gt;
 &lt;br&gt; Phone number:
 &lt;input type=&quot;text&quot; name=&quot;mobileno&quot; size=&quot;30&quot;&gt;
 &lt;br&gt;
 &lt;br&gt;
 &lt;input type=&quot;submit&quot; value=&quot;Submit&quot;&gt;
 &lt;input type=&quot;reset&quot; value=&quot;Clear All&quot;&gt;
 &lt;/p&gt;
 &lt;/form&gt;
&lt;/body&gt;

&lt;/html&gt;
</code></pre>
</div>

<div>
@Chris, 
 
I thought the same thing re the format - however if you look at the output from his opening post the Query is coming through as 
 

<pre><code class="code-1 nolinks" id="code-20-42542143-1">Error: INSERT INTO signin (F_name,U_name,password,email,DOB,phn)VALUES ('kkkk','qqqqq','77777','mmmmmmmmm','/2017-03-24/','10000000')
Incorrect date value: '/2017-03-24/' for column 'DOB' at row 1 
</code></pre>
The YYYY-MM-DD input format would explain the other errors but not where the leading / trailing '/' in the final query string are coming from. ['/2017-03-24/']
</div>

<div>
On top of what Julian has said (dump your POST), you need to change lines 18-20 to the following: 
 

<pre><code class="code-1 nolinks" id="code-20-42542146-1">$rawDoB = new DateTime($_POST['DOB']);
$DOB = $rawDoB-&gt;format(&quot;y-m-d&quot;); // this will format your date to yyyy-mm-dd. Change according to your needs.
</code></pre>
</div>

<div>
@Julian - good point. Along with the result and the undefined index, it's almost as if the DOB array is being concatenated with the slash - NULL/DOB[0]/NULL !! 
 
Odd !
</div>

<div>
I tried to replicate with his code and sending different DOB strings to it - couldn't get the results. That is why I think there is more to this than we are seeing.
</div>

<div>
$date = $_POST['DOB']; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$explode = explode(&quot;/&quot;, $date); 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$month &nbsp;= $explode[0]; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$day = $explode[1]; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$year = $explode[2]; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$all = $month.&quot;-&quot;.$year.&quot;-&quot;.$day; 
&nbsp;that's the way I fixed it
</div>

<div>
That makes no sense, breaking it up like that does not change anything - it is functionally the same as what you had to begin with. 
I would still go with either my recommendation where 

<pre><code class="code-1 nolinks" id="code-20-42542161-1">$date = isset($_POST['DOB']) ? $_POST['DOB'] : false;
if ($date) {
 $dob = date('Y-m-d', strtotime($date);
 ...
}
</code></pre>
Or Chris'
<pre><code class="code-1 nolinks" id="code-20-42542161-2">$rawDoB = new DateTime($_POST['DOB']);
$DOB = $rawDoB-&gt;format(&quot;y-m-d&quot;); // this will format your date to yyyy-mm-dd. Change according to your needs.
</code></pre>
 
There are functions for doing what you want to do - you don't need to go re-inventing the wheel to do what is already available.
</div>

<div>
Well that doesn't really make sense, but glad you got it sorted !
</div>

<div>
I don't understand the accepted solution. 
The advice given in that solution is just plain wrong - it is stating that the inclusion of the array variables in the string is incorrect and concatenation should be used - but this is misleading - as the original string has nothing wrong with it.
</div>

<div>
Hi @ Julian Hansen 
 
He want to insert date in other format 
am just suggest him 
 
Is there any problem or mistake in my solution 
so please tell me 
 
and I think it is not a bad solution 
Thank You
</div>

<div>
btw, storing passwords is eval (<a href="http://plaintextoffenders.com/faq/devs" rel="ugc">Plain Text Offenders</a>). Or at least a huge security issues. Store a salted (per user) hash instead. See <a href="http://php.net/manual/en/faq.passwords.php" rel="ugc">Safe Password Hashing</a>.
</div>

<div>
<blockquote>
Is there any problem or mistake in my solution
</blockquote>
You posted this 

<blockquote>
&lt;?php 
&nbsp;$DOB=$_POST['DOB']; 
&nbsp; &nbsp; &nbsp; $DOB = explode(&quot;/&quot;,$DOB); 
&nbsp; &nbsp; &nbsp; $DOB = &quot;$DOB[2]-$DOB[0]-$DOB[1]&quot;; 
This is wrong method 
?&gt;
</blockquote>
Stating that what is being done here is wrong. This is incorrect - there is nothing wrong with the above and is definitely not the cause of the errors specified in the original post. 
You recommended 

<blockquote>
&lt;?php 
&nbsp; $DOB=$_POST['DOB']; 
&nbsp; &nbsp; &nbsp; $DOB = explode(&quot;/&quot;,$DOB); 
&nbsp; &nbsp; &nbsp; $DOB = $DOB[2].&quot;-&quot;.$DOB[0].&quot;-&quot;.$DOB[1]; 
This is correct way to change your / to - 
?&gt;
</blockquote>
Stating this is the correct way - which is also misleading (as I pointed out in <a href="https://www.experts-exchange.com/questions/29095935/Date-of-birth-insertion-insertion-in-mysql-through-php.html?anchorAnswerId=42541959#a42541959" rel="ugc">my post</a>) 
There is nothing wrong with embedding array variables (or any other variable) in a string - and to say that concatenation is the right way and variable embedding is the wrong way is not correct. 
 
We still don't know what the problem was here - we are guessing it was bad input but without more information from the author we cannot say. 
 
The fact that splitting up the exploded items &quot;fixed&quot; the problem - simply does not make sense - that does not explain the original errors.
</div>

<div>
I'm with Julian on this - the accepted solution is not the solution to the problem. The problem was not caused by the string builder: 
 
$DOB = &quot;$DOB[2]-$DOB[0]-$DOB[1]&quot;; 
 
is functionally identical to this: 
 
$DOB = $DOB[2].&quot;-&quot;.$DOB[0].&quot;-&quot;.$DOB[1]; 
 
so switching one out for the other does absolutely nothing for the functionality of the code.
</div>

<div>
<div class="content wysiwyg-content">
I am having a problem while inserting the Date of Birth field's value from html form to mysql datebase using the php. I have used the input type 'date' in html to get the input. 
&lt;?php 
&nbsp; &nbsp; &nbsp; &nbsp;$DOB=$_POST['DOB']; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$DOB = explode(&quot;/&quot;,$DOB); 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$DOB = &quot;$DOB[2]-$DOB[0]-$DOB[1]&quot;; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$sql = &quot;INSERT INTO signin (F_name,U_name,password,email,DOB,phn)VALUES ('$F_name','$U_name','$password','$email','$DOB','$phn')&quot;; 
?&gt; 
&lt;html 
DOB:&lt;input type=&quot;date&quot; name=&quot;DOB&quot; size=&quot;20&quot;&gt;&lt;br&gt;&lt;br&gt; 
/html&gt; 
 
output error: 
( ! ) Notice: Undefined offset: 2 in C:\wamp64\www\Blogger\signin.php on line 20 
Call Stack 
# &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Time &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Memory &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Function &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Location 
1 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.0004 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;248128 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{main}( ) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...\signin.php:0 
 
( ! ) Notice: Undefined offset: 1 in C:\wamp64\www\Blogger\signin.php on line 20 
Call Stack 
# &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Time &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Memory &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Function &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Location 
1 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.0004 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;248128 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{main}( ) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...\signin.php:0 
Error: INSERT INTO signin (F_name,U_name,password,email,DOB,phn)VALUES ('kkkk','qqqqq','77777','mmmmmmmmm','/2017-03-24/','10000000') 
Incorrect date value: '/2017-03-24/' for column 'DOB' at row 1
</div>
</div>

I am having a problem while inserting the Date of Birth field's value from html form to mysql datebase using the php. I have used the input type 'date' in html to get the input.
<?php
 $DOB=$_POST['DOB'];
	$DOB = explode("/",$DOB);
	$DOB = "$DOB[2]-$DOB[0]-$DOB[1]";
	$sql = "INSERT INTO signin (F_name,U_name,password,email,DOB,phn)VALUES ('$F_name','$U_name','$password','$email','$DOB','$phn')";
?>
<html
DOB:<input type="date" name="DOB" size="20"> 
/html>

output error:
( ! ) Notice: Undefined offset: 2 in C:\wamp64\www\Blogger\signin.php on line 20
Call Stack
#	Time	Memory	Function	Location
1	0.0004	248128	{main}( )	...\signin.php:0

( ! ) Notice: Undefined offset: 1 in C:\wamp64\www\Blogger\signin.php on line 20
Call Stack
#	Time	Memory	Function	Location
1	0.0004	248128	{main}( )	...\signin.php:0
Error: INSERT INTO signin (F_name,U_name,password,email,DOB,phn)VALUES ('kkkk','qqqqq','77777','mmmmmmmmm','/2017-03-24/','10000000')
Incorrect date value: '/2017-03-24/' for column 'DOB' at row 1

Date of birth insertion insertion in mysql through php.

HTML (HyperText Markup Language) is the main markup language for creating web pages and other information to be displayed in a web browser, providing both the structure and content for what is sent from a web server through the use of tags. The current implementation of the HTML specification is HTML5.

HTML

PHP is a widely-used server-side scripting language especially suited for web development, powering tens of millions of sites from Facebook to personal WordPress blogs. PHP is often paired with the MySQL relational database, but includes support for most other mainstream databases. By utilizing different Server APIs, PHP can work on many different web servers as a server-side scripting language.

datetime

MySQL is an open source, relational database management system that runs as a server providing multi-user access to a number of databases. Acquired by Oracle in 2009, it is frequently used in combination with PHP installations, powering most of the WordPress installations.