{"id":2340,"date":"2021-07-21T14:16:08","date_gmt":"2021-07-21T14:16:08","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=2340"},"modified":"2021-07-21T14:16:10","modified_gmt":"2021-07-21T14:16:10","slug":"php-serialize","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-serialize\/","title":{"rendered":"PHP serialize"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to the PHP serialize()<\/code> function to serialize an object.<\/p>\n\n\n\n

Introduction to the PHP serialize() function #<\/a><\/h2>\n\n\n\n

To serialize an object<\/a> into a string<\/a>, you use the serialize()<\/code> function:<\/p>\n\n\n

serialize(mixed $value): string<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The serialize()<\/code> function returns a string that contains a byte-stream representation of the object. And you can store this string in storage such as a file or a database.<\/p>\n\n\n\n
For example, the following defines the Customer<\/code> class:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Customer<\/span>\n<\/span>{\n\n    private<\/span> $id;\n\n    private<\/span> $name;\n\n    private<\/span> $email;\n\n    public<\/span> function<\/span> __construct<\/span>(int $id, string $name, string $email)<\/span>\n    <\/span>{\n        $this<\/span>->id = $id;\n        $this<\/span>->name = $name;\n        $this<\/span>->email = $email;\n    }\n\n    public<\/span> function<\/span> getInitial<\/span>()<\/span>\n    <\/span>{\n        if<\/span> ($this<\/span>->name !== ''<\/span>) {\n            return<\/span> strtoupper(substr($this<\/span>->name, 0<\/span>, 1<\/span>));\n        }\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
And this illustrates how to use the serialize()<\/code> function to serialize a Customer<\/code> object:<\/p>\n\n\n
<?php<\/span>\n\nrequire<\/span> 'Customer.php'<\/span>;\n\n$customer = new<\/span> Customer(10<\/span>, 'John Doe'<\/span>, 'john.doe@example.com'<\/span>);\n$str = serialize($customer);\n\nvar_dump($str);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
string(132<\/span>) \"O:8:\"<\/span>Customer\":3:{s:12:\"<\/span>Customerid\";i:10;s:14:\"<\/span>Customername\";s:8:\"<\/span>John Doe\";s:15:\"<\/span>Customeremail\";s:20:\"<\/span>john.doe@example.com\";}\"<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Notice that the serialize()<\/code> function only serializes the properties of the object, not the method.<\/p>\n\n\n\n
The following example serializes a Customer<\/code> object and saves the string to a file:<\/p>\n\n\n
<?php<\/span>\n\nrequire<\/span> 'Customer.php'<\/span>;\n\n$customer = new<\/span> Customer(10<\/span>, 'John Doe'<\/span>, 'john.doe@example.com'<\/span>);\n$str = serialize($customer);\n\nfile_put_contents('customer.dat'<\/span>, $str);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The __sleep() magic method #<\/a><\/h3>\n\n\n\n
The serialize()<\/code> function checks if the class implements the __sleep()<\/code> method. If so, it’ll execute the __sleep()<\/code> method before serializing the object.<\/p>\n\n\n
public<\/span> __sleep(): array<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The __sleep()<\/code> method returns an array that contains property names that will be serialized.<\/p>\n\n\n\n
If the __sleep()<\/code> method doesn’t return anything, the serialize()<\/code> function will serialize null value and issue an E_NOTICE<\/code>.<\/p>\n\n\n\n
The following example illustrates how to implement the __sleep()<\/code> method:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Customer<\/span>\n<\/span>{\n    private<\/span> $id;\n    private<\/span> $name;\n    private<\/span> $email;\n\n    public<\/span> function<\/span> __construct<\/span>(int $id, string $name, string $email)<\/span>\n    <\/span>{\n        $this<\/span>->id = $id;\n        $this<\/span>->name = $name;\n        $this<\/span>->email = $email;\n    }\n\n    public<\/span> function<\/span> getInitial<\/span>()<\/span>\n    <\/span>{\n        if<\/span> ($this<\/span>->name !== ''<\/span>) {\n            return<\/span> strtoupper(substr($this<\/span>->name, 0<\/span>, 1<\/span>));\n        }\n    }\n\n    public<\/span> function<\/span> __sleep<\/span>()<\/span>: array<\/span>\n    <\/span>{\n        return<\/span> ['id'<\/span>, 'name'<\/span>];\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the __sleep()<\/code> method returns an array that contains the names of the id and name properties. And the serialize()<\/code> function will only serialize the values of these properties:<\/p>\n\n\n
<?php<\/span>\n\nrequire<\/span> 'Customer.php'<\/span>;\n\n$customer = new<\/span> Customer(10<\/span>, 'John Doe'<\/span>, 'john.doe@example.com'<\/span>);\n$str = serialize($customer);\n\nvar_dump($str);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
string(81<\/span>) \"O:8:\"<\/span>Customer\":2:{s:12:\"<\/span>Customerid\";i:10;s:14:\"<\/span>Customername\";s:8:\"<\/span>John Doe\";}\"<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In practice, you would want to encrypt sensitive information such as email and credit card numbers before carrying the serialization.<\/p>\n\n\n\n
The __serialize() magic method #<\/a><\/h3>\n\n\n\n
The __serialize()<\/code> method is similar to the __sleep()<\/code> method:<\/p>\n\n\n
public<\/span> __serialize(): array<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
However, the __serialize()<\/code> method returns an associative array of key\/value pairs representing the object’s serialized form.<\/p>\n\n\n\n
Also, if the __serialize()<\/code> method doesn’t return an array, PHP will throw a TypeError<\/code>.<\/p>\n\n\n\n
For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Customer<\/span>\n<\/span>{\n    private<\/span> $id;\n\n    private<\/span> $name;\n\n    private<\/span> $email;\n\n    public<\/span> function<\/span> __construct<\/span>(int $id, string $name, string $email)<\/span>\n    <\/span>{\n        $this<\/span>->id = $id;\n        $this<\/span>->name = $name;\n        $this<\/span>->email = $email;\n    }\n\n    public<\/span> function<\/span> getInitial<\/span>()<\/span>\n    <\/span>{\n        if<\/span> ($this<\/span>->name !== ''<\/span>) {\n            return<\/span> strtoupper(substr($this<\/span>->name, 0<\/span>, 1<\/span>));\n        }\n    }\n\n    public<\/span> function<\/span> __serialize<\/span>()<\/span>: array<\/span>\n    <\/span>{\n        return<\/span> [\n            'id'<\/span> => $this<\/span>->id,\n            'name'<\/span> => $this<\/span>->name,\n        ];\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The following illustrates how to use the serialize()<\/code> function to serialize a Customer<\/code> object:<\/p>\n\n\n
<?php<\/span>\n\nrequire<\/span> 'Customer.php'<\/span>;\n\n$customer = new<\/span> Customer(10<\/span>, 'John Doe'<\/span>, 'john.doe@example.com'<\/span>);\n$str = serialize($customer);\n\nvar_dump($str);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
If a class has both __serialize()<\/code> and __sleep()<\/code> method, the serialize()<\/code> function calls the __serialize()<\/code> method only and ignores the __sleep()<\/code> method.<\/p>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Use the serialize()<\/code> function to serialize an object into a string of byte-stream representation.<\/li>
  • Use the __sleep()<\/code> or __serialize()<\/code> method to implement the logic before serialization.<\/li><\/ul>\n
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