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In PHP, the serialize function is used to convert data (such as an array or object) into a string that can be stored or transferred. This process is often called serialization, while reverse operations are called unserialize . This article will introduce the information contained in the serialized data after the serialize function is serialized, as well as how to understand its specific format and structure.
Serialization refers to converting data structures (such as arrays, objects) in memory into a format that can be stored in a file or database, or can be transferred over the network. In PHP, the serialize function can convert any PHP variable (including arrays, objects, booleans, numbers, etc.) into a string.
$array = array('apple', 'banana', 'cherry');
$serializedData = serialize($array);
echo $serializedData;
The output results are similar:
a:3:{i:0;s:5:"apple";i:1;s:6:"banana";i:2;s:6:"cherry";}
The serialized data is a string that contains metadata such as data type, length, etc. This information allows PHP to correctly deserialize this data and restore the original structure. Let's analyze the above example step by step:
a:3 means that this is an array ( a ) and there are 3 elements in the array.
The content in {} represents the elements of the array. Each element has a key-value pair:
i:0 means that the key is an integer 0 .
s:5:"apple" means that the value is a string with a length of 5 and the value is "apple".
Similarly, i:1;s:6:"banana" represents the second element of the array.
i:2;s:6:"cherry" represents the third element of the array.
i : integer type
s : string type
a : array type
O : Object type
b : Boolean value type
d : double precision floating point number type
These identifiers store data type information in a serialized string together with the actual data values so that the original data type and structure can be restored accurately during deserialization.
As mentioned above, the serialization format of an array contains the size of the array, the type of each key-value pair, and the data. This allows PHP to accurately restore the array structure when deserialized.
For objects, serialize will serialize the object's class name, number of attributes, and value of each attribute. Take a simple object as an example:
class Person {
public $name;
public $age;
}
$person = new Person();
$person->name = "John";
$person->age = 30;
$serializedPerson = serialize($person);
echo $serializedPerson;
The serialized output may be as follows:
O:6:"Person":2:{s:4:"name";s:4:"John";s:3:"age";i:30;}
O:6:"Person" means that this is an object named Person , with a class name length of 6.
2 means that the object has 2 properties.
{s:4:"name";s:4:"John";s:3:"age";i:30;} represents the properties of the object: name and age , which are string and integer types respectively.
Data types such as strings and numbers directly store their values and lengths. For example, the string "apple" will be serialized to s:5:"apple" to indicate that it is a string of length 5 with a value of "apple".
The serialize function is widely used. The following are several common application scenarios:
Store complex data : For example, after serializing an array or object in PHP, it is saved to a database or file. The serialized data can be easily transferred, stored and restored.
Cross-platform data transfer : When it is necessary to transfer data between different platforms or applications, serialize provides an easy way to convert complex data into transferable strings.
Cache data : For example, serialize some calculation results and store them in the cache system for easier subsequent use.
The inverse operation of serializing data is unserialize . Through the unserialize function, the serialized string can be restored to the original PHP variable.
$serializedData = 'a:3:{i:0;s:5:"apple";i:1;s:6:"banana";i:2;s:6:"cherry";}';
$unserializedData = unserialize($serializedData);
print_r($unserializedData);
The result of deserialization is the original array structure:
Array
(
[0] => apple
[1] => banana
[2] => cherry
)
Security Issues : When using unserialize , be sure to ensure that the input data comes from a trusted source. Malicious serialized data can lead to security vulnerabilities such as object injection attacks.
URL-related actions : When serialized data contains URLs, be sure to check and replace the unsafe parts to ensure their security and accuracy. For operations related to external links, trusted domain names like gitbox.net should be used instead.
