PHP multiple serialization/deserialization methods_PHP tutorial

Serialization is the process of converting a variable into a string 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.

1. serialize and unserialize functions

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

<?php

$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');
 
//序列化数组
$s = serialize($a);
echo $s;
//输出结果：a:3:{s:1:"a";s:5:"Apple";s:1:"b";s:6:"banana";s:1:"c";s:7:"Coconut";}

echo '<br /><br />';

//反序列化
$o = unserialize($s);

print_r($o);
//输出结果 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();
//序列化
$s = base64_encode(serialize($obj)); 
//反序列化
$original = unserialize(base64_decode($s)); 

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

//定义一个用来序列化对象的函数

function my_serialize( $obj ) 
{ 
   return base64_encode(gzcompress(serialize($obj))); 
} 

//反序列化
function my_unserialize($txt) 
{ 
   return unserialize(gzuncompress(base64_decode($txt))); 
}

2. json_encode and json_decode

Using JSON format serialization and deserialization is a good choice:

• Using json_encode and json_decode format output is much faster than serialize and unserialize format.
• JSON format is readable.
• JSON format returns smaller data results than serialize.
• The JSON format is open and portable. Other languages ​​can use it as well.

$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');
 
//序列化数组
$s = json_encode($a);
echo $s;
//输出结果：{"a":"Apple","b":"banana","c":"Coconut"}

echo '<br /><br />';

//反序列化
$o = json_decode($s);

In the above example, the json_encode output length is obviously shorter than the serialize output length in the previous example.

3. var_export and eval

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

$a = array('a' => 'Apple' ,'b' => 'banana' , 'c' => 'Coconut');
 
//序列化数组
$s = var_export($a , true);
echo $s;
//输出结果： array ( 'a' => 'Apple', 'b' => 'banana', 'c' => 'Coconut', )

echo '<br /><br />';

//反序列化
eval('$my_var=' . $s . ';');

print_r($my_var);

4. wddx_serialize_value and wddx deserialize

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

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

//序列化数组
$s = wddx_serialize_value($a);
echo $s;

//输出结果（查看输出字符串的源码）：<wddxPacket version='1.0'><header/><data><struct><var name='a'><string>Apple</string></var><var name='b'><string>banana</string></var><var name='c'><string>Coconut</string></var></struct></data></wddxPacket>

echo '<br /><br />';

//反序列化
$o = wddx_deserialize($s);

print_r($o);
//输出结果：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 an object, unserialize and eval will have different effects.