Write an application that reads in a five-digit integer and determines whether it’s a palindrome. If the number is not five digits long, display an error message and allow the user to enter a new value.

I used many functions in this script. like Mod, Divide, Array Value Assigning, Float Function, then I used simple If .. else.. If conditional statement, and if within in statement.  
(Palindromes) A palindrome is a sequence of characters that reads the same backward as
forward.
For example, each of the following five-digit integers is a palindrome: 12321, 55555, 45554 and
11611.

Try this code. I hope you will learn from it.

---

 <?PHP  
      $inputs = array();  
      if (isset($_POST['submit'])) { //to check if the form was submitted  
           $value = isset($_POST['input0'])? $_POST['input0'] : null;  
           for($count = 1; $value != null; $count++){  
                array_push($inputs, $value);  
                $value = isset($_POST['input'.$count])? $_POST['input'.$count] : null;  
           }  
      }  
      var_dump($inputs);  
 ?>       
 <form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">  
   <!-- to take multiple inputs copy the below line and change name="input" attribute -->  
   Enter input 1:&nbsp;<input type="text" name="input0" value="" /><br />  
   <input type="submit" name="submit" value="Submit" />  
 </form>  
 <?php  
 $dig = $inputs[0];  
 /*Now I need to get Mod 5th times from remaining value*/  
   $dig5 = ($dig % 10); //as mod of 10201 is 1 : $dig5 is Digit 5  
     $inputs[5] = $dig5; //1 is saved in 5th index  
   $dig4 = ($dig / 10); //value like 1020.1 : $dig4 is Digit 4  
     $dig4v = floor($dig4); //It will make 1020 : $dig4v is Digit 4th Value  
       $dig4vi = ($dig4v % 10); // as Mode of 1020 is 0 : $dig4vi is Digit 4th value index  
         $inputs[4] = $dig4vi; //0 is saved in 4th index  
   $dig3 = ($dig4v / 10); //value like 102.0 : $dig3 is Digit 3  
     $dig3v = floor($dig3); //It will make 102 : $dig3v is Digit 3rd Value  
       $dig3vi =($dig3v % 10); // as Mode of 102 is 2 : $dig3vi is Digit 3rd value index  
          $inputs[3] = $dig3vi; //2 is saved in 3rd index  
   $dig2 = ($dig3v / 10); //value like 10.2 : $dig2 is Digit 2  
     $dig2v = floor($dig2); //It will make 10 : $dig2v is Digit 2nd Value  
       $dig2vi = ($dig2v % 10); // as Mode of 10 is 0 : $dig2vi is Digit 2nd value index  
         $inputs[2] = $dig2vi; //0 is saved in 2rd index  
   $dig1 = ($dig2v / 10); //value like 1.0 : $dig1 is Digit 1  
     $dig1v = floor($dig1); //It will make 1 : $dig1v is Digit 1st Value  
       $inputs[1] = $dig1v; //1 is saved in 1st index  
 if (($inputs[0]>=10000)&&($inputs[0]<=99999))  
   {       
       if(($inputs[1]==$inputs[5])&&($inputs[2]==$inputs[4]))  
         {  
           echo "{$inputs[0]} is a palindrome number. <br />";  
         }  
       elseif(($inputs[1]!=$inputs[5])||($inputs[2]!=$inputs[4]))  
         {  
           echo "{$inputs[0]} is not a palindrome number. <br />";  
         }                                          
   }                           
 else  
   {  
     echo "Try Again : Enter 5 Digit Number. :(";  
   }  
 ?>