Serialization/UnSerialization:

  • Generates a storable representation of a value.
  • serialize() returns a string containing a byte-stream representation of any value that can be stored in PHP. 
  • unserialize() can use this string to recreate the original variable values.
  • This process makes a storable representation of a value that is useful for storing or passing PHP values.
  • To make the serialized string into a PHP value again, use unserialize().

Before starting your serialization process, PHP will execute the __sleep function automatically. This is a magic function or method.
Before starting your unserialization process, PHP will execute the __wakeup function automatically. This is a magic function or method.


What can you Serialize and Unserialize?
  • Variables
  • Arrays
  • Objects 
What cannot you Serialize and Unserialize?
  • Resource-type
Example:
//BaseClass.php
<?php

  class BaseClass {
      public $var = 100;
    
      public function show() {
          echo $this->var;
      }
  }
  
// test1.php:


  include("BaseClass.php");
  
  $a = new A;
  $v = serialize($a);
  file_put_contents('store_in_var', $v);


// page2.php:
  
  include("BaseClass.php");
  $v = file_get_contents('store_in_var');
  $a = unserialize($v);




  $a->show();
?>

 In the Case if you want to store entire array into database then with serialze() it would be useful to store an entire array in a field in a database.
You can pass an array to the function, and it will return a string that is essentially the string. 
You can then unserialize() it to obtain the full array once again.


example:


<?php

$str_array = array( "Rajesh Sharma", "Rajesh", "RajeshS" );
$serialized_str = serialize($str_array);
echo $serialized_str;


?>


This will output a:3:{i:0;s:14:"Rajesh Sharma";i:1;s:6:"Rajesh";i:2;s:7:"RajeshS";}
so you can store entire array in a field in a database.


<?php

$str_array = array( "Rajesh Sharma", "Rajesh", "RajeshS" );
$serialized_str = serialize($str_array);


print_r(unserialize($serialized_str));


?>
This will output a Array ( [0] => Rajesh Sharma[1] => Rajesh [2] => RajeshS ).