Preallocate string memory in PHP

Is it possible to preallocate memory for a string in PHP or to set a string to a constant fixed size?

I have a random string that is generated, it's always 32 chars long, and it currently concatenates a character on the end of the string; I'm th开发者_如何学Pythoninking that it would be more efficient if I could use a constant sized string.

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You could use str_repeat() to pre-generate a string containing 32 spaces, and, then, access each character like this :

$string[3] = 'a';

Note: see String access and modification by character in tha manual, about that.

I suppose it would cause less memory (re-)allocations.

But, really :

• you shouldn't worry about that kind of micro-optimization...
• I'm not sure how strings are implemented in PHP (you'd have to take a look at its source-code), so not sure this idea would be better for performances.