PHP Tutorial-Deserialization Method

Serialization is the process of converting variables into strings that can be saved or transmitted; deserialization is to convert this string into the original variable at the appropriate time for use. These two processes combine to easily store and transfer data, making the program more maintainable. Brothers PHP training (www.lampbrother.net)



1. serialize and unserialize functions



These two are common functions for serializing and deserializing data in PHP.


$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');

//Serialization Array

$s = serialize($a);

echo $s;

//Output result: a:3:{s:1:"a";s:5:"Apple";s:1: "b";s:6:"banana";s:1:"c";s:7:"Coconut";}

echo '

';

/ /Deserialization

$o = unserialize($s);

print_r($o);

//Output result Array ( [a] => Apple [b] => banana [c] => ; Coconut )

?>

When array values ​​contain characters such as double quotes, single quotes, or colons, problems may occur after they are deserialized. To overcome this problem, a neat trick is to use base64_encode and base64_decode.

$obj = array();

//Serialization

$s = base64_encode(serialize($obj));

//Deserialization

$original = unserialize(base64_decode($s));

But base64 encoding will increase the length of the string. To overcome this problem, it can be used with gzcompress.

//Define a function for serializing objects

function my_serialize( $obj )

{

Return base64_encode(gzcompress(serialize($obj)));

}

//Deserialization

function my_unserialize($txt)

{

return unserialize(gzuncompress(base64_decode($txt)));

}

2. json_encode and json_decode



Use JSON format to serialize and decode Serialization is a Good choice:



Using json_encode and json_decode format output is much faster than serialize and unserialize formats.

JSON format is readable.

JSON format returns smaller data than serialize.

The JSON format is open and portable. Other languages ​​can use it as well.

$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');

//Serialized array

$s = json_encode($a);

echo $s;

//Output result: {"a":"Apple","b":"banana","c":"Coconut"}

echo '
';

//Deserialization

$o = json_decode($s);

In the above example, the json_encode output length is obviously longer than the serialize output length in the previous example Be short.



3. var_export and eval



var_export function outputs the variable as a string; eval executes the string as a PHP code, and deserializes to obtain the content of the original variable.



$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');



//Serialized array



$s = var_export($a , true);



echo $s;



//Output result: array ( 'a' => 'Apple', 'b' => ' banana', 'c' => 'Coconut', )



echo '

';



//Deserialization



eval(' $my_var=' . $s . ';');



print_r($my_var);

4. wddx_serialize_value and wddx deserialize



wddx_serialize_value function can serialize array variables and output them as XML strings .



$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');



//Serialized array

$s = wddx_serialize_value($a);

echo $s;



//Output result (view the source code of the output string):

bananaCoconut< ;/string>



echo '

';



// Deserialization

$o = wddx_deserialize($s);

print_r($o);

//Output result: Array ( [a] => Apple [b] => banana 1 => Coconut )

It can be seen that there are many XML tag characters, so the serialization of this format still takes up a lot of space.



Summary



All the above functions can be executed normally when serializing array variables, but it is different when applied to objects. For example, json_encode serialized objects will fail. When deserializing objects, unserialize and eval will have different effects.