PHP array serialization where values implement Serializable

Question

I'm running into a weird issue where if I try to serialize an array of objects of the same class, where that class has implemented the Serializable interface and in the serializable interface returns the serialized instance of another class, the array items after the first couple are considered recursive.

Here is a test case:

<?php

class HelloWorld implements Serializable {
    public $test;

    public function __construct($str)
    {
        $this->test = $str;
    }

    public function serialize()
    {
        $simple = null;
        $simple = new Simple();
        $simple->test = $this->test;
        return serialize($simple);
    }

    public function unserialize($str)
    {
        $simple = unserialize($str);
        $this->test = $simple->test;
    }
}

class Simple
{
    public $test;
}

$list = array(
    new HelloWorld('str1'),
    new HelloWorld('str2'),
    new HelloWorld('str3'),
    new HelloWorld('str4'),
    new HelloWorld('str5'),
    new HelloWorld('str6'),
    new HelloWorld('str7'),
    new HelloWorld('str8'),
    new HelloWorld('str9'),
);

$str = serialize($list);
echo $str . "\n";

// var_dump(unserialize($str));

Uncomment the last line and enjoy a php segmentation fault.

Does anyone know why this is or how to fix it? This doesn't seem to be an issue if what is being serialized in HelloWorld::serialize() is an array or a primitive value.

Update:

Here is the output from the above code:

a:9:{i:0;C:10:"HelloWorld":39:{O:6:"Simple":1:{s:4:"test";s:4:"str1";}}i:1;C:10:"HelloWorld":4:{r:3;}i:2;C:10:"HelloWorld":4:{r:3;}i:3;C:10:"HelloWorld":4:{r:3;}i:4;C:10:"HelloWorld":4:{r:3;}i:5;C:10:"HelloWorld":4:{r:3;}i:6;C:10:"HelloWorld":4:{r:3;}i:7;C:10:"HelloWorld":4:{r:3;}i:8;C:10:"HelloWorld":4:{r:3;}}

The issue is the r:4; stuff on the second and following records.

César · Accepted Answer · 2013-12-13 21:03:00Z

1

DAMN! Sorry, I read your question wrong. Thought you wanted to print all of them.

You need simple to be serializable. Otherwise it won't work, in order to serialize you need could use something like this:

class HelloWorld implements Serializable 
{
    public $test;

    public function __construct($str)
    {
         $this->test = $str;
    }

    public function serialize()
    {
        return serialize($this->test);
    }

    public function unserialize($str)
    {
        $simple = unserialize($str);
        $this->test = $simple;
    }
}

The simple class is not needed. Remember that $this->data will always have to be serializable.

edited Dec 13, 2013 at 21:03

answered Dec 13, 2013 at 20:36

César

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2 Comments

will_in_wi Over a year ago

My example code is simplified from the original case to better illustrate the issue and remove some of our supporting libraries from the equation. In my original codebase, HelloWorld corresponds to a model class. Simple corresponds to a generic data-only class for templates. The reason I want the two classes like this is so that on unserialize, I can recreate the database connections. This is legacy code, so I can't rearchitect it.

César Over a year ago

It's perfectly fine. You just have to make sure that the Simple class is serializable and you will just be able to serialize and unserialize at will (without rebuilding the object). You can recreate the database connections when unserializing. That's exactly what I do in my code.

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