Checking input string is Palindrome or not with Demo

Enter any string

Check a string by comparing it with its reverse

A simple palindrome check compares a normalized string with strrev(). For user input, initialize the form value safely and escape it before placing it back into HTML.

$text = 'racecar';
if ($text === strrev($text)) {
    echo 'Palindrome';
}

Checking string or number is Palindrome or not using PHP sticky form without strrev() functions

We used strrev() to reverse a string and then compare. We can use a form to post the string to the script. This is sticky form holding the value of user entered data. Here is the complete code.

<form method=POST action='' name=form1>
<input type=text name=t1 class='form-control' value='$t1' >
<input type=submit value='Check String'>
</form>
<?Php
$t1=$_POST['t1'] ?? ''; // Using POST method  of a FORM 
//$t1='madam'; // String variable with data for testing
if(strlen($t1) >0){
  if($t1==strrev($t1)){ // change this line  for case insensitive 
   echo "<i>$t1</i> is a Palindrome ";
  }else{
   echo "<i>$t1</i> is NOT a Palindrome ";
  }
}else{echo "Enter any string"; }
?>

case insensitive

We can use strtolower() function to convert all upper case chars to lower case char before using the if condition checking. Here is the change in if condition ( of above used code ) to make it case insensitive.

if(strtolower($t1)==strtolower(strrev($t1))){

Without using strrev()

We can use for loop to read each char from the end of the string. The function strlen() returns the length of the string.

<?php
$t1='racecar';  // sample string, change this data 
$length=strlen($t1); // length of the string
$t1_reverse=''; // to hold the revesed string
for($i=$length-1;$i>=0;$i--){
$t1_reverse .=$t1[$i];
}
if($t1_reverse==$t1){
echo "<i>$t1</i> is a Palindrome ";	
}else{
echo "<i>$t1</i> is NOT a Palindrome ";		
}
?>

Using Numbers

We can get digits out of number and get the reverse number from the main number.

<?php
$t1=$t2=1234321; // keeping in two variables 
$t1_reverse=0; 
while($t1>0){
	$d=$t1%10; // reminder of division 
	$t1_reverse = $t1_reverse * 10 + $d;
	$t1=floor($t1/10); // floor value
}
//echo $t1_reverse;

if($t1_reverse==$t2){
echo "<i>$t2</i> is a Palindrome ";	
}else{
echo "<i>$t2</i> is NOT a Palindrome ";		
}
?>

Output

1234321 is a Palindrome

Introduction to PHP Printing output by ECHO command
Basic Codes Armstrong number Fibonacci Series

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

About the author Watch on YouTube

Connect:

Subscribe to our YouTube Channel here

PHP Palindrome checking

Check a string by comparing it with its reverse

case insensitive

Without using strrev()

Using Numbers

Subhendu Mohapatra