PHP str_rot13() Function Last Updated : 11 Jul, 2025 Comments Improve Suggest changes Like Article Like Report The function str_rot13() is a built-in function in php. This function accepts a string and shifts every alphabet present in the string by 13 places in the alphabet. The function leaves numeric and non-alphabetical characters untouched. By passing an encoded string as argument, the function will return the original string. Syntax: str_rot13 ( $string ) Parameter: This function accepts only a string parameter which can be observed from the above syntax. The description of the parameter is as follows. $string : This is the only mandatory parameter of the function. This parameter passes a string to the function which needs to be encoded. Return Value: The function returns the encoded string. Examples: Input : $string = "Geeks for Geeks" Output : Trrxf sbe Trrxf Input : $string = "Trrxf sbe Trrxf" Output : Geeks for Geeks Below program illustrate the str_rot13() function in PHP: php <?php echo str_rot13("Geeks for Geeks"); echo "\n"; echo str_rot13("Trrxf sbe Trrxf"); ?> Output: Trrxf sbe Trrxf Geeks for Geeks Reference: https://www.php.net/manual/en/function.str-rot13.php Create Quiz Comment GeeksforGeeks 0 Improve GeeksforGeeks 0 Improve Article Tags : Misc Web Technologies PHP PHP-string Explore BasicsPHP Syntax4 min readPHP Variables5 min readPHP | Functions6 min readPHP Loops4 min readArrayPHP Arrays5 min readPHP Associative Arrays4 min readMultidimensional arrays in PHP5 min readSorting Arrays in PHP4 min readOOPs & InterfacesPHP Classes2 min readPHP | Constructors and Destructors5 min readPHP Access Modifiers4 min readMultiple Inheritance in PHP4 min readMySQL DatabasePHP | MySQL Database Introduction4 min readPHP Database connection2 min readPHP | MySQL ( Creating Database )3 min readPHP | MySQL ( Creating Table )3 min readPHP AdvancePHP Superglobals6 min readPHP | Regular Expressions12 min readPHP Form Handling4 min readPHP File Handling4 min readPHP | Uploading File3 min readPHP Cookies9 min readPHP | Sessions7 min read Like