serialize

(PHP 4, PHP 5, PHP 7, PHP 8)

serialize — Genera una versione archiviabile del valore

Descrizione

serialize(mixed $value): string

Genera una versione archiviabile di un valore

Questo è utile per archiviare o passare valori a PHP senza perderne il tipo e la struttura.

Per ottenere il valore dalla stringa serializzata, utilizzare la funzione unserialize().

Elenco dei parametri

value

Il valore da serializzare. serialize() gestisce tutti i tipi di variabili tranne il tipo resource. Possono essere elaborati da serialize() array che contengano riferimenti a se stessi. Saranno archiviati anche i riferimenti circolari negli array/object. Ogni altro riferimento verrà perso.

Quando si esegue la serializzazione di oggetti, PHP cerca di eseguire la funzione __sleep prima di cominciare la serializzazione. Questo permette all'oggetto di eseguire le ultime operazioni di chiusura prima di essere serializzato. Analogamente, quando l'oggetto viene ripristinato usando unserialize() viene chiamata la funzione membro __wakeup.

Nota:
I membri privati dell'oggetto avranno il nome della classe preposto al nome del membro; i membri protetti avranno un '*' preposto al nome del membro. Questi valori preposti sono delimitati da byte null.

Valori restituiti

Restituisce una stringa contenente un flusso di bytes rappresentante value che può essere archiviato ovunque.

Esempi

Example #1 Esempio di serialize()

<?php
// L'array multi-dimensionale $session_data contiene le informazioni della sessione
// per l'utente. Si userà serialize() per memorizzare le informazioni
// all'interno di un database alla fine della richiesta..

$conn = odbc_connect("webdb", "php", "chicken");
$stmt = odbc_prepare($conn,
      "UPDATE sessions SET data = ? WHERE id = ?");
$sqldata = array (serialize($session_data), $_SERVER['PHP_AUTH_USER']);
if (!odbc_execute($stmt, $sqldata)) {
    $stmt = odbc_prepare($conn,
     "INSERT INTO sessions (id, data) VALUES(?, ?)");
    if (!odbc_execute($stmt, $sqldata)) {
        /* Qualcosa non ha funzionato... */
    }
}
?>

Log delle modifiche

Versione	Descrizione
4.0.7	Il processo di serializzazione degli oggetti è stato corretto.

Note

Nota:
It is not possible to serialize PHP built-in objects.

Vedere anche:

unserialize() - Crea un valore PHP a partire da una rappresentazione archiviata
Serializing Objects

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User Contributed Notes 7 notes

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363

egingell at sisna dot com ¶

18 years ago

<?
/*
Anatomy of a serialize()'ed value:

 String
 s:size:value;

 Integer
 i:value;

 Boolean
 b:value; (does not store "true" or "false", does store '1' or '0')

 Null
 N;

 Array
 a:size:{key definition;value definition;(repeated per element)}

 Object
 O:strlen(object name):object name:object size:{s:strlen(property name):property name:property definition;(repeated per property)}

 String values are always in double quotes
 Array keys are always integers or strings
    "null => 'value'" equates to 's:0:"";s:5:"value";',
    "true => 'value'" equates to 'i:1;s:5:"value";',
    "false => 'value'" equates to 'i:0;s:5:"value";',
    "array(whatever the contents) => 'value'" equates to an "illegal offset type" warning because you can't use an
    array as a key; however, if you use a variable containing an array as a key, it will equate to 's:5:"Array";s:5:"value";',
     and
    attempting to use an object as a key will result in the same behavior as using an array will.
*/
?>

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281

Anonymous ¶

12 years ago

Please! please! please! DO NOT serialize data and place it into your database. Serialize can be used that way, but that's missing the point of a relational database and the datatypes inherent in your database engine. Doing this makes data in your database non-portable, difficult to read, and can complicate queries. If you want your application to be portable to other languages, like let's say you find that you want to use Java for some portion of your app that it makes sense to use Java in, serialization will become a pain in the buttocks. You should always be able to query and modify data in the database without using a third party intermediary tool to manipulate data to be inserted. 

I've encountered this too many times in my career, it makes for difficult to maintain code, code with portability issues, and data that is it more difficult to migrate to other RDMS systems, new schema, etc. It also has the added disadvantage of making it messy to search your database based on one of the fields that you've serialized. 

That's not to say serialize() is useless. It's not... A good place to use it may be a cache file that contains the result of a data intensive operation, for instance. There are tons of others... Just don't abuse serialize because the next guy who comes along will have a maintenance or migration nightmare.

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mark at bvits dot co dot uk ¶

1 year ago

There is a type not mentioned in the user notes so far, 'E'.  This is the newer Enum class that can be utilised:

login_security|E:25:"Permission:manageClient"

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MC_Gurk at gmx dot net ¶

18 years ago

If you are going to serialie an object which contains references to other objects you want to serialize some time later, these references will be lost when the object is unserialized.
The references can only be kept if all of your objects are serialized at once.
That means:

$a = new ClassA(); 
$b = new ClassB($a); //$b containes a reference to $a;

$s1=serialize($a);
$s2=serialize($b);

$a=unserialize($s1);
$b=unserialize($s2);

now b references to an object of ClassA which is not $a. $a is another object of Class A.

use this:
$buf[0]=$a;
$buf[1]=$b;
$s=serialize($buf);
$buf=unserialize($s);
$a=$buf[0];
$b=$buf[1];

all references are intact.

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nh at ngin dot de ¶

11 years ago

Serializing floating point numbers leads to weird precision offset errors:

<?php

echo round(96.670000000000002, 2);
// 96.67

echo serialize(round(96.670000000000002, 2));
// d:96.670000000000002;

echo serialize(96.67);
// d:96.670000000000002;

?>

Not only is this wrong, but it adds a lot of unnecessary bulk to serialized data. Probably better to use json_encode() instead (which apparently is faster than serialize(), anyway).

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Andrew B ¶

12 years ago

When you serialize an array the internal pointer will not be preserved. Apparently this is the expected behavior but was a bit of a gotcha moment for me. Copy and paste example below.



<?php

//Internal Pointer will be 2 once variables have been assigned.

$array = array();

$array[] = 1;

$array[] = 2;

$array[] = 3;



//Unset variables. Internal pointer will still be at 2.     

unset($array[0]);

unset($array[1]);

unset($array[2]);



//Serialize

$serializeArray = serialize($array);



//Unserialize

$array = unserialize($serializeArray);



//Add a new element to the array

//If the internal pointer was preserved, the new array key should be 3.

//Instead the internal pointer has been reset, and the new array key is 0.

$array[] = 4;



//Expected Key - 3

//Actual Key - 0

echo "<pre>" , print_r($array, 1) , "</pre>";

?>

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frost at easycast dot ru ¶

11 years ago

Closures cannot be serialized:
<?php
$func = function () {echo 'hello!';};
$func(); // prints "hello!"

$result = serialize($func);  // Fatal error: Uncaught exception 'Exception' with message 'Serialization of 'Closure' is not allowed' 
?>

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