Standard Palindrome in PHP

A palindrome is a word or phrase that reads the same forwards and backwards, ignoring spaces and punctuation. “Racecar”, “level”, and “A man a plan a canal Panama” are all palindromes.

Here’s a PHP script that checks whether a string is a standard palindrome by stripping non-alphanumeric characters, lowercasing, and comparing the result against its reverse.

The PHP Code

Replace $originalPalindromeToTest with the string you want to check:

<?php
$originalPalindromeToTest = "Madam I'm Adam";
$palindrome = strtolower(preg_replace("([^A-Za-z0-9])", "", $originalPalindromeToTest ));
$palindromeReversed = strtolower(strrev($palindrome));
echo "Original Statement: $originalPalindromeToTest <br /><br />";

if ($palindrome == $palindromeReversed){
echo "$palindrome is a Standard Palindrome of $palindromeReversed";
}else{
echo "$palindrome is <strong>not</strong> a Standard Palindrome of $palindromeReversed";
};
?>

How It Works

The script runs three operations on the input before comparing:

• Strip non-alphanumeric characters: preg_replace removes anything that isn’t a letter or number (spaces, apostrophes, punctuation, etc.). “Madam I’m Adam” becomes “MadamImAdam”.
• Lowercase: strtolower converts the cleaned string so the comparison is case-insensitive. “MadamImAdam” becomes “madamimadam”.
• Reverse: strrev reverses the cleaned string. “madamimadam” reversed is still “madamimadam”.

If the cleaned string matches its reverse, it’s a palindrome. The if statement prints the result either way.

Example Output

Running the script with “Madam I’m Adam” prints:

Original Statement: Madam I'm Adam

madamimadam is a Standard Palindrome of madamimadam

With a non-palindrome like “hello”:

Original Statement: hello

hello is not a Standard Palindrome of olleh

Reusable Function Version

If you need to check multiple strings, wrapping the logic in a function is cleaner and easier to reuse across your codebase:

<?php
function isPalindrome(string $str): bool {
    $cleaned = strtolower(preg_replace('/[^A-Za-z0-9]/', '', $str));
    return $cleaned === strrev($cleaned);
}

var_dump(isPalindrome("racecar"));                      // bool(true)
var_dump(isPalindrome("Madam I'm Adam"));               // bool(true)
var_dump(isPalindrome("hello"));                        // bool(false)
var_dump(isPalindrome("A man a plan a canal Panama"));  // bool(true)
?>

This version uses === for strict comparison and standard forward-slash regex delimiters. It returns a boolean you can drop directly into any conditional.

If you’re working with PHP strings more broadly, limiting text length in PHP is another handy snippet for string handling.