PHP: Does it make sense to create constant arrays to increase performance?

Question

I need to perform many str_replace($search, $replace, $input) using the same $search and $replace. These are exploded in a function:

function sr($input) {

    $search = explode(",","s1,s2,s3,....");
    $replace = explode(",","r1,r2,r3,...");

    return str_replace($search, $replace, $input);

}

It is not very efficient. From another SO question, I see that I could create constant arrays, but the suggested method implies serialization. I bet this is not efficient too, but am I right?

I have a compiled language mindset, so whenever I can make something constant, I am happy. But does it make sense in PHP? I am not a PHP pro.

More precisely, knowing that this function is going to be used when users make web requests to a page, how can I optimize explodes efficiently? Is there any such thing as precompiled code in PHP? Or can I define constant arrays once for all, efficiently (like testing whether the constant is already created/available in the context)?

UPDATE

Taking Truth's suggestion into account, we can modify the function as following:

function sr($input) {

    $search = array("s1","s2","s3",....");
    $replace = array("r1","r2","r3",...");

    return str_replace($search, $replace, $input);

}

The remaining question is: is it optimal to declare these arrays at each call or could should we try to create them as constants in the context?

There are PHP compilers, but not all PHP scripts can be compiled. — Marc B, Mar 15 '12 at 17:07
I don't see the point of explode. Why don't you just set `$search = array("s1", "s2", "s3", ....);`? — Madara's Ghost, Mar 15 '12 at 17:08
@Truth Yes you have point, I just lack experience in PHP. I am updating my question — Jérôme Verstrynge, Mar 15 '12 at 17:10
You could use `static` keyword for that purpose, but I have any info if it would have impact on performance. — Bartosz Grzybowski, Mar 15 '12 at 17:16

Your Common Sense · Accepted Answer · 2012-03-15T17:25:47.680

10

Does it make sense to [take random action right off your head] to increase performance?

No.

Start worrying about performance only if you have certain performance problem.
Once you've got it - start profiling.
Once you've got certain profiling results pointing to certain bottleneck - start optimizing that bottleneck.
Repeat until done.

edited Mar 15 '12 at 17:25

answered Mar 15 '12 at 17:14

Your Common Sense

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Assuming we hit a bottleneck, how would you answer my question? – Jérôme Verstrynge Mar 15 '12 at 17:20
What he means is you can't think about optimization if you don't understand where the performance problem is - and if it really exists. – Daniel Ribeiro Mar 15 '12 at 17:20
2

@JVerstry easy-peasy. I'd avoid performing many str_replace on each user's request. – Your Common Sense Mar 15 '12 at 17:22

PHP: Does it make sense to create constant arrays to increase performance?

1 Answers1

No.