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<?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( $pattern, fn($m) => $lookup[array_key_last($m)], $file_content ) );
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