PHP, Mathematical Functions


<?php



string|false base64_decode ( string $string, bool $strict = false )





where,





$string = The base64 encoded to be decoded



$strict = To control whether there are characters 

              inside or outside the Base64 alphabet.





?>

$string

The base64 encoded to be decoded.

$strict

If $strict = TRUE this functions returns FALSE if $string contains character from outside the base64 alphabet.

Otherwise invalid characters will be silently discarded.

Returns the decoded data or FALSE on failure.

The returned data may be binary.

BASE64 alphabet

base64_encode Is designed to allow binary data transfer in 8-bit layers to be handled in layers that are not truly 8-bit.

Base64 alphabet
0	A	16	Q	32	g	48	w
1	B	17	R	33	h	49	x
2	C	18	S	34	i	50	y
3	D	19	T	35	j	51	z
4	E	20	U	36	k	52	0
5	F	21	V	37	l	53	1
6	G	22	W	38	m	54	2
7	H	23	X	39	n	55	3
8	I	24	Y	40	o	56	4
9	J	25	Z	41	p	57	5
10	K	26	a	42	q	58	6
11	L	27	b	43	r	59	7
12	M	28	c	44	s	60	8
13	N	29	d	45	t	61	9
14	O	30	e	46	u	62	+
15	P	31	f	47	v	63	/
						64	=
ed48

EXERCISE


<?php



$strbase64_it_02 =

'Li4uIMOoIGJlbmUgdHJvdmF0byE=';



$str_it_02 = 

base64_decode($strbase64_it_02);



echo $str_it_02



?>

RESULT

Li4uIMOoIGJlbmUgdHJvdmF0byE=

...è bene trovato!

EXERCISE


<?php



$fp = fopen('starpx.dat', "r");

$img_str = fread($fp, 8000);

fclose($fp);



?>

<img src="data:image/png;base64, <?php echo $img_str; ?>" alt="star apr">

EXERCISE


<?php



echo "Decode an input string containing the 

                    whole base64 alphabet:<br><br>";

                    

$allbase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ

              abcdefghijklmnopqrstuvwxyz

              0123456789

              +/VV==";



var_dump(bin2hex(base64_decode($allbase64)));

echo '<br><br>';

var_dump(bin2hex(base64_decode($allbase64, false)));

echo '<br><br>';

var_dump(bin2hex(base64_decode($allbase64, true)));



?>

EXERCISE


<?php



echo "Decode 'hello world!':<br><br>";



$noWhiteSpace = "aGVsbG8gd29ybGQh";

var_dump(base64_decode($noWhiteSpace));

echo '<br><br>'; 

var_dump(base64_decode($noWhiteSpace, false));

echo '<br><br>'; 

var_dump(base64_decode($noWhiteSpace, true));



echo "<br><br>Whitespace does not affect base64_decode, 

                          even with \$strict===true:<br>";

$withWhiteSpace = "a GVs   bG8gd2

                        9ybGQh";

var_dump(base64_decode($withWhiteSpace));

echo '<br><br>'; 

var_dump(base64_decode($withWhiteSpace, false));

echo '<br><br>'; 

var_dump(base64_decode($withWhiteSpace, true));



echo "<br><br>Other chars outside the base64 alphabet 

                    are ignored when \$strict===false, 

                    but cause failure with \$strict===true:<br>";

$badChars = $noWhiteSpace . '*';

var_dump(base64_decode($badChars));

echo '<br><br>'; 

var_dump(base64_decode($badChars, false));

echo '<br><br>'; 

var_dump(base64_decode($badChars, true));



?>