<?php
echo preg_replace_callback('~[A-Z]~', function($_) { return $_ + 32; }, 'Important: you are NOT allowed to use a built-in function that converts the string (or just one character) to lowercase (such as ToLower() in .NET, strtolower() in PHP , ...)! You\'re allowed to use all other built-in functions, however.');
Fatal error: Uncaught TypeError: Unsupported operand types: array + int in /in/ZF5Vo:2
Stack trace:
#0 [internal function]: {closure}(Array)
#1 /in/ZF5Vo(2): preg_replace_callback('~[A-Z]~', Object(Closure), 'Important: you ...')
#2 {main}
thrown in /in/ZF5Vo on line 2
Process exited with code 255.
Fatal error: Uncaught Error: Unsupported operand types in /in/ZF5Vo:2
Stack trace:
#0 [internal function]: {closure}(Array)
#1 /in/ZF5Vo(2): preg_replace_callback('~[A-Z]~', Object(Closure), 'Important: you ...')
#2 {main}
thrown in /in/ZF5Vo on line 2
Process exited with code 255.