Is there a encoding function in PHP which will encode strings and the resulting output will only contain letters and numbers? I would use base64 but that still has some stuff which is not numeric/alphanumeric
+1
A:
Any of the hash functions (md5, sha1, etc.) output will only consist of hexadecimal digits but that's not exactly 'encoding'.
Nev Stokes
2010-10-29 08:07:00
Don't want to hash because it needs to be recoverable.
cappuccino
2010-10-29 08:18:46
I know it's an additional step but can't you hash the string again when you need to recover the key for the APC cache?
Nev Stokes
2010-10-29 08:41:51
Why does an APC key need to be recoverable? It's a cache, fetching with a one-way encoding seems pretty OK to me?
Wrikken
2010-10-29 08:50:10
A:
You can use the basic md5 hash function which output only alphanumeric characters.
gulbrandr
2010-10-29 08:08:22
Yeah, and its counterpart `md5_decode()` ;) Seriously though, it looks like the OP is looking for an encode / decode pair, not a hashing function
Pekka
2010-10-29 08:09:34
that's not an answer, if you don't like to invest the time for a real answer, don't post. This is SO, not some kind of forum.
tharkun
2010-10-29 08:14:14
@tharkun: sorry about that. I thought it was enough as the md5 documentation is clear. I edited my answer.
gulbrandr
2010-10-29 08:31:50
A:
It really depends on your goal. Please explain in more detail what you want to achieve!
If you mean encoding in the sense of charset, then I doubt there is a charset that contains only alphanumeric members. base64 stands for a set of encodings limited to 64 chars, which is more than just the alphanumeric chars.
If you want to get rid of everything non-alphanumeric, I would suggest validating/filtering the content. You can use existing filter mechanism like in Zend_Validate or you can write your own filter. You can use Regular Expressions for this.
tharkun
2010-10-29 08:12:23
Its to be used as the key to my APC cache objects, APC key's can't contain things other than a-z, 0-9 and i think underscores.
cappuccino
2010-10-29 08:20:09
+3
A:
You could use base32 (code easy to google), which is sort of a standard alternative to base64. Or resort to bin2hex() and pack("H*",$hex) to reverse. Hex encoding however leads to size doubling.
mario
2010-10-29 08:44:16
(but if its of any significant size, and starting off as text, you can compress it first!)
symcbean
2010-10-29 08:48:32
A:
You could write your own base-62 encoder/decoder using a-z/A-Z/0-9. You'd need 3 digits for every ASCII character though, so not that efficient.
Mike C
2010-10-29 08:47:27
+1
A:
Short answer is no, base64 uses a reduced set of output chars compared with uuencode and was intended to solve most character converions issues - but still isn't url-safe (IIRC).
But the machanism is trivial and easily adapted - I'd suggest having a look at base32 encoding - same as base64 but using one less bit per input char to create the output (and hence a 32 char alphabet is all that's required) but using something different for the padding char ('=' is not url safe).
A quick google found this
symcbean
2010-10-29 08:47:50