Online PHP editor | output for BsGGM

<?php $file_content = "Employees are employees_category MyEmployees kitEMPLOYEESMATCH"; $f = 'employees'; $r = 'vehicles'; $pattern = '~(' . implode( ')|(', [ preg_quote($f, '~'), preg_quote(ucfirst($f), '~'), preg_quote(strtoupper($f), '~') ] ) . ')~'; $lookup = [ 1 => $r, 2 => ucfirst($r), 3 => strtoupper($r) ]; var_export( preg_replace_callback( $pattern, function($m) use ($lookup) { return $lookup[count($m) - 1]; }, $file_content ) );