is eval() function expensive?

[Anon]

i was told that eval() function reduces performance because php works by having a parser which parses the code in to some kind of parse-tree, then an interpreter which goes through the parse tree line-by-line executing the commands. so when php hits an eval() function it will be operating in interpreter mode, but will then be forced to jump back in to parse mode to analyse the string, before jumping back again in to interpreter mode to execute it. if this is the case what can i do instead of eval my code which is stored in a database?

[Anon]

In your case, eval() is the only function you can use. eval() may be a bit more expensive, but as long as you don't use it too much in one script, it should be ok.

Diego

[Anon]

can you explain why eval is expensive? can i for instance preg_replace out my strings etc? but for me that is more difficult.

[Anon]

If you want to have reusable chunks of code your best bet is to create your own functions and store them in a file which you can include(). If your code must be in a db then eval() is the only way to go but this is a bit slower.