Serializing is a nice way to get a string out of more complicated data structure. It's probably mostly used to sting-alize array data, although you can serialize scalar data as well.
The result of the serialization is no nature wonder, it's just a string that describes what is serialized and a value of the serialized ... thing.
The cert guide explains it all very well, I think just maybe an example of how something looks when it's serialized would have been nice. Otherwise the serialization may sound scary and mysterious.
Here's an example:
$s = 'PHP';
- 's' is a string, the type of the serialized var
- '3' is the length
- 'PHP' is the value
- ';' is a delimiter
A slightly more complicated example - serializing an array:
$ar = array('PHP','key'=>'serialize');
The result is:
- 'a' means an array
- 'i' as in integer
- 'i:0' is the integer key of the first element of the array, remember when you don't specify a key, PHP assigns one