PHP | Palindrome Check
In this article, we will learn how to check whether a number and a string is a palindrome or not in PHP. A number or string is said to be a palindrome if it remains same even after reversing the digits or letters respectively.
Examples for Palindrome Number:
Input : 1441 Output : Palindrome Explanation: Reversing 1441 will also get 1441 Input : 12521 Output : Palindrome Explanation remains same
Check for Palindrome number
Here we have simply used the iterative way to check for the palindrome number. Each digit is extracted in an iteration and formed the reverse number and finally, it is checked, whether it is same as the original number.
Check for Palindrome String
Examples for Palindrome String:
Input : "MALAYALAM" Output : Palindrome Explanation: Reversing "MALAYALAM" will also get "MALAYALAM" Input : "14441" Output : Palindrome Explanation remains same
Method 1: Using strrev()
The strrev() function is used in PHP to reverse a string. We can simply use this method to reverse the string and match it with the previous value. If it is a match, then the string is palindrome else not.
Method 2: Recursive way using substr()
The substr() method is used to return a part of a string, referred to as the substring. Using this method, there is a recursive way to check for Palindrome or not. In this method no new string is formed and the original string is modified in each recursive call.
The first character is matched with the last character of the string during each recursive call and if it matches, then both the characters are discarded during the next call. This goes on until the length of the string reduces to 0 or 1. In the following example where the word “MALAYALAM”, is taken, let’s see the working.
In the first step both the M’s at both, the end is compared. Since it matches, both of them are discarded and the next string to be passed is “ALAYALA”. Again both the A matched at both the end, so next string to be passed is “LAYAL”. This goes on until only “Y” remains.