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POregain constant pseudo-random in PHP 5.2
 

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  1. POregain constant pseudo-random in PHP 5.2
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    <p>I am including the same "random.inc" in foo.php and bar.php. For each, I want reproducible "random" results. </p> <p>So in foo.php I always want one set of numbers and/or keywords. In bar.php another. Which shouldn't change on reload. That's what I mean by <strong>contant</strong> pseudo-random. And that's why I seeding on the url. However I still get different results for individual numbers as well as for array pickson every reload. This is the full php file:</p> <pre><code>&lt;? header('Content-Type: text/plain'); $seed = crc32( $_SERVER['REQUEST_URI'] ); echo "phpversion: ".phpversion()."\nseed: $seed\n"; srand( $seed ); // (seed verified to be contant as expected) // neither single values nor array pics turn out deterministic echo ''.rand(0,100).' '.rand(0,100).' '.rand(0,100)."\n"; $values = array( '0'=&gt;21,'1'=&gt;89,'2'=&gt;96,'3'=&gt;47,'4'=&gt;88 ); print_r( array_rand( $values, 3 ) ); ?&gt; </code></pre> <p>In the days of PHP4.1 it was (verified) possible to achieve constant pseudo-random like this. <a href="http://php.net/manual/en/function.array-rand.php" rel="nofollow">array_rand API documentation</a> describes as a feature that since 4.2 initialization happens automatically. Perhaps this is overriding any explicit seeding? (if so, perhaps explicit seeding should raise an internal PHP flag, preventing automatic seeding?). Btw: mt_srand() and srand() are equally not working.</p> <p>I would really like to get my <em>deterministic</em> / <em>constant</em> pseudo-random back...</p> <p><strong>Update:</strong> Solution below (Windows and/or version 5.2 's fault)</p>
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    1. COWhat are you trying to do with the random function here?
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      1. USDogbert
    2. CO`array_rand()` still responds to a preset `srand()` for me. PHP5.3.3/amd64
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    3. CO(There is only pseudo-random. There is no such thing as random.)
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      1. USRudie
 

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