PHP manual by official site (www.php.net) (available in many languages: English, Brazilian Portuguese, Chinese (Simplified), Chinese (Hong Kong Cantonese), Chinese (Traditional), Czech, Danish, Dutch, Finnish, French, [Special French], German, Greek, Hebrew, Hungarian, Italian, Japanese, Korean, Polish, Romanian, Russian, Slovak, Spanish, Swedish)

PHP manual by PHP PlanetMirror (php.planetmirror.com): online reading (available in Italian)