How to use php serialize() and unserialize()

Question

A PHP array or object or other complex data structure cannot be transported or stored or otherwise used outside of a running PHP script. If you want to persist such a complex data structure beyond a single run of a script, you need to serialize it. That just means to put the structure into a "lower common denominator" that can be handled by things other than PHP, like databases, text files, sockets. The standard PHP function serialize is just a format to express such a thing, it serializes a data structure into a string representation that's unique to PHP and can be reversed into a PHP object using unserialize. There are many other formats though, like JSON or XML.

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Take for example this common problem:

How do I pass a PHP array to Javascript?

PHP and Javascript can only communicate via strings. You can pass the string "foo" very easily to Javascript. You can pass the number 1 very easily to Javascript. You can pass the boolean values true and false easily to Javascript. But how do you pass this array to Javascript?

Array ( [1] => elem 1 [2] => elem 2 [3] => elem 3 ) 

The answer is serialization. In case of PHP/Javascript, JSON is actually the better serialization format:

{ 1 : 'elem 1', 2 : 'elem 2', 3 : 'elem 3' }

Javascript can easily reverse this into an actual Javascript array.

This is just as valid a representation of the same data structure though:

a:3:{i:1;s:6:"elem 1";i:2;s:6:"elem 2";i:3;s:7:" elem 3";}

But pretty much only PHP uses it, there's little support for this format anywhere else.
This is very common and well supported as well though:

<array>
    <element key='1'>elem 1</element>
    <element key='2'>elem 2</element>
    <element key='3'>elem 3</element>
</array>

There are many situations where you need to pass complex data structures around as strings. Serialization, representing arbitrary data structures as strings, solves how to do this.

PHP serialize() unserialize() usage

http://freeonlinetools24.com/serialize

echo '<pre>';
// say you have an array something like this 
$multidimentional_array= array(
    array(
        array("rose", 1.25, 15),
        array("daisy", 0.75, 25),
        array("orchid", 4, 7) 
       ),
    array(
        array("rose", 1.25, 15),
        array("daisy", 0.75, 25),
        array("orchid", 5, 7) 
       ),
    array(
        array("rose", 1.25, 15),
        array("daisy", 0.75, 25),
        array("orchid", 8, 7) 
    )
);

// serialize 
$serialized_array=serialize($multidimentional_array);
print_r($serialized_array);

Which gives you an output something like this

a:3:{i:0;a:3:{i:0;a:3:{i:0;s:4:"rose";i:1;d:1.25;i:2;i:15;}i:1;a:3:{i:0;s:5:"daisy";i:1;d:0.75;i:2;i:25;}i:2;a:3:{i:0;s:6:"orchid";i:1;i:4;i:2;i:7;}}i:1;a:3:{i:0;a:3:{i:0;s:4:"rose";i:1;d:1.25;i:2;i:15;}i:1;a:3:{i:0;s:5:"daisy";i:1;d:0.75;i:2;i:25;}i:2;a:3:{i:0;s:6:"orchid";i:1;i:5;i:2;i:7;}}i:2;a:3:{i:0;a:3:{i:0;s:4:"rose";i:1;d:1.25;i:2;i:15;}i:1;a:3:{i:0;s:5:"daisy";i:1;d:0.75;i:2;i:25;}i:2;a:3:{i:0;s:6:"orchid";i:1;i:8;i:2;i:7;}}}

again if you want to get the original array back just use PHP unserialize() function

$original_array=unserialize($serialized_array);
var_export($original_array);

I hope this will help

<?php
$a= array("1","2","3");
print_r($a);
$b=serialize($a);
echo $b;
$c=unserialize($b);
print_r($c);

Run this program its echo the output

a:3:{i:0;s:1:"1";i:1;s:1:"2";i:2;s:1:"3";}

---

here
a=size of array
i=count of array number
s=size of array values

you can use serialize to store array of data in database
and can retrieve and UN-serialize data to use.

When you want to make your php value storable, you have to turn it to be a string value, that is what serialize() does. And unserialize() does the reverse thing.

Most storage mediums can store string types. They can not directly store a PHP data structure such as an array or object, and they shouldn't, as that would couple the data storage medium with PHP.

Instead, serialize() allows you to store one of these structs as a string. It can be de-serialised from its string representation with unserialize().

If you are familiar with json_encode() and json_decode() (and JSON in general), the concept is similar.