What's the maximum key length for PHP APC?

Question

You would think this would be super-easy to find, but I can't seem to.

score 7 · Answer 1 · answered Jul 25 '13 at 14:45

7

There appears to be no limitation on key size/content.

Internally, keys are initialized via the C function apc_cache_make_user_key, which takes the given key string ("identifier") and stores it along with a hashed version.

answered Jul 25 '13 at 14:45

Steve Clay

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score 2 · Accepted Answer · answered May 05 '11 at 00:36

2

I really don't know PHP, but it looks like values are added using apc_add() or apc_store(), which take keys which are strings. I would infer that the maximum key length is therefore the maximum length of a string in PHP.

According to PHP: Strings,

Note: It is no problem for a string to become very large. PHP imposes no boundary on the size of a string; the only limit is the available memory of the computer on which PHP is running.

answered May 05 '11 at 00:36

Matt Ball

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@Steve Clay: Agreed, and thanks for your actual answer. Very long keys are more likely to exhaust APC's allotted shared memory space (default=32M) before PHP (or even the system) runs out of memory. – Zilk Aug 14 '13 at 00:00

What's the maximum key length for PHP APC?

2 Answers2