Question: I need to store:

```
array(1,2,3,4,5);

```

into a mysql blob.

How can i convert this array into binary data?

Answer: 
It depends mostly on how you are using those informations. IDs are usually used to identify a resource, and thus must be unique, not null and indexable.

> 
> By those standarts do not use as blob.
> 
> 
> 

Mostly because search by content is slower than as native variable. Also, SQL databases sort the content of a table to ensure faster queries.

If what you need is just storing information and then using another ID to identify this resource (and they can be easily parsed to strings/numbers then do not use blob). A binary file will usually use 8 bytes per char. A number could contain the same information using less total memory. Example, 1902334123 (random keyboard smash) uses 10\*8 = 80 bytes in Hard disk, while an 32-bit signed integer could hold it.

Finally, if what you need is just storing several data units, what is your problem with a sequential varchar to be read as string, as it could solve your problem
you can convert to JSON and store to db:

```
json_encode($array);

```

and when you return from db:

```
json_decode($array);

```