PHP Program to Reverse String with Example

You can reverse a string in PHP using the built-in function strrev(), for example: $reversed = strrev($string);.

Examples

Inputhello

Outputolleh

InputPHP

OutputPHP

Input

Output

How to Think About It

To reverse a string, think of reading the characters from the end to the start. PHP provides a simple function strrev() that does this by taking the input string and returning a new string with characters in reverse order.

Algorithm

1

Get the input string.

2

Use the built-in function to reverse the string.

3

Return or print the reversed string.

Code

php

<?php
$string = "hello";
$reversed = strrev($string);
echo $reversed;
?>

Output

olleh

Dry Run

Let's trace the string "hello" through the code.

1

Input string

$string = "hello"

2

Reverse string

$reversed = strrev("hello"); // returns "olleh"

3

Output result

echo "olleh"

Step	Value of string	Value of reversed
1	hello
2	hello	olleh
3	hello	olleh

Why This Works

Step 1: Using strrev()

The strrev() function takes a string and returns a new string with characters in reverse order.

Step 2: Assign reversed string

We store the reversed string in a variable to use or print later.

Step 3: Print the result

Using echo outputs the reversed string to the screen.

Alternative Approaches

Manual loop reversal

php

<?php
$string = "hello";
$reversed = "";
for ($i = strlen($string) - 1; $i >= 0; $i--) {
    $reversed .= $string[$i];
}
echo $reversed;
?>

This method manually builds the reversed string by looping backward; it is more verbose but helps understand the process.

Using array functions

php

<?php
$string = "hello";
$array = str_split($string);
$reversedArray = array_reverse($array);
$reversed = implode('', $reversedArray);
echo $reversed;
?>

This method converts the string to an array, reverses it, then joins it back; useful for learning array manipulation.

Complexity: O(n) time, O(n) space

Time Complexity

The function processes each character once, so time grows linearly with string length.

Space Complexity

A new string is created to hold the reversed characters, so space also grows linearly.

Which Approach is Fastest?

Using strrev() is fastest and simplest; manual loops or array methods are slower and more complex.

Approach	Time	Space	Best For
strrev()	O(n)	O(n)	Quick and simple reversal
Manual loop	O(n)	O(n)	Learning how reversal works
Array functions	O(n)	O(n)	Practicing array manipulation