(PHP 4, PHP 5)

serializeGenerates a storable representation of a value


string serialize ( mixed $value )

Generates a storable representation of a value

This is useful for storing or passing PHP values around without losing their type and structure.

To make the serialized string into a PHP value again, use unserialize().



The value to be serialized. serialize() handles all types, except the resource-type. You can even serialize() arrays that contain references to itself. Circular references inside the array/object you are serializing will also be stored. Any other reference will be lost.

When serializing objects, PHP will attempt to call the member function __sleep prior to serialization. This is to allow the object to do any last minute clean-up, etc. prior to being serialized. Likewise, when the object is restored using unserialize() the __wakeup member function is called.


Object's private members have the class name prepended to the member name; protected members have a '*' prepended to the member name. These prepended values have null bytes on either side.

Return Values

Returns a string containing a byte-stream representation of value that can be stored anywhere.


Example #1 serialize() example

// $session_data contains a multi-dimensional array with session
// information for the current user.  We use serialize() to store
// it in a database at the end of the request.

$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)) {
/* Something went wrong.. */


Version Description
4.0.7 The object serialization process was fixed.



Note that many built-in PHP objects cannot be serialized. However, those with this ability either implement the Serializable interface or the magic __sleep and __wakeup methods. If an internal class does not fulfill any of those requirements, it cannot reliably be serialized.

There are some historical exceptions to the above rule, where some internal objects could be serialized without implementing the interface or exposing the methods. Notably, the ArrayObject prior to PHP 5.2.0.

See Also

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