PHP实现base64_encode

根据base64编码规则，用代码实现base64_encode功能

$str = 'AS156SSEFSS';$input = str_split($str,1);$base = array();$base = array_merge($base,range('A','Z'));$base = array_merge($base,range('a', 'z'));$base = array_merge($base,range(0,9));array_push($base, '+');array_push($base, '/');$ret = array();foreach ($input as $key => $value) {array_push($ret, sprintf("%'.08d",base_convert(ord($value), 10, 2)));}$str = implode('', $ret);$in = str_split($str,6);foreach ($in as $key => $value) {$in[$key] = str_pad($value, 6,'0',STR_PAD_RIGHT);}$out = array();foreach ($in as $key => $value) {array_push($out, $base[base_convert($value, 2, 10)]);}while (count($out)%4!=0) {array_push($out, '=');}return implode('', $out);