Randomly generating a character?

Question

I'm randomly generating chars in PHP, using:

for ($i = 0; $i < $length; $i++) {  
    $generatedCode .= chr(rand(97, 122));  
}

But I dont want the letters "g" and "m" to be in the randomly generated string, how can I do this?

http://stackoverflow.com/questions/853813/how-to-create-a-random-string-using-php — pleasedontbelong, Oct 27 '11 at 14:25

deceze · Accepted Answer · 2011-10-27T14:41:34.947

9

$chars = array_diff(range('a', 'z'), array('g', 'm'));

$generatedCode = '';
for ($i = 0; $i < $length; $i++) {  
    $generatedCode .= $chars[array_rand($chars)];
}

edited Oct 27 '11 at 14:41

answered Oct 27 '11 at 14:25

deceze

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OP, doing loops until you hit the right char is wrong. This is what you need. – Leonid Shevtsov Oct 27 '11 at 14:27
I would clean it up slightly with `while (strlen($generatedCode) < $length) { ... }` instead of introducing a counting variable, but this is still the best solution. – user229044 Oct 27 '11 at 14:36
@meagar Computationally that's slightly more expensive though, so... meh. :) – deceze Oct 27 '11 at 14:39
@deceze You assume, but I doubt it. I've benchmarked this assumption in the past, and it's no longer true, if it ever was *in PHP*. It is not a language for micro-optimization. – user229044 Oct 27 '11 at 14:40
1

@meagar It's not much, but a little... http://codepad.org/kG59sxEM :) It certainly isn't worth discussing about, whichever style floats your boat is fine. – deceze Oct 27 '11 at 14:44

score 2 · Answer 2 · edited Oct 27 '11 at 14:28

2

for ($i = 0; $i < $length; $i++) {
    do {
        $randChar = chr(rand(97, 122));
    } while($randChar != 'g' && $randChar != 'm');
    $generatedCode .= $randChar;
}

edited Oct 27 '11 at 14:28

user229044

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answered Oct 27 '11 at 14:25

Emir Akaydın

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score 1 · Answer 3 · edited Oct 27 '11 at 14:26

1

Do the loop until the correct values are in place.

for ($i = 0; $i < $length;) {  
    $code = chr(rand(97, 122));  
    if ($code !== 'm' && $code !== 'g') // add the correct values here
    {
         $i++
         $generatedCode .= $code;
    }
}

edited Oct 27 '11 at 14:26

user229044

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answered Oct 27 '11 at 14:24

Rene Pot

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score 1 · Answer 4 · answered Oct 27 '11 at 14:26

Put simply, filter out 'g' and 'm';

<?php
$length = 8;
$generatedCode = '';
while( strlen( $generatedCode ) < $length ) {  
    $random = chr(rand(97, 122));
    if( !in_array( $random, array( 'g', 'm' ) ) ) {
        $generatedCode .= $random;  
    }
}

echo $generatedCode;

score 0 · Answer 5 · answered Oct 27 '11 at 14:23

0

for ($i = 0; $i < $length; $i++) {  
    $generated = chr(rand(97, 122));
    if ($generated != "g" && $generated != "m") {
       $generatedCode .= $generated;  
    }
    else{
       $i--;
    }
}

answered Oct 27 '11 at 14:23

genesis

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The `else $i--` is kind of ugly. Why not only increment in the correct case, instead of incrementing every time and decrementing in the incorrect case? – user229044 Oct 27 '11 at 14:27
+1 @meagar - why not `while (in_array($generated = chr(rand(97, 122)),array('g','m'))) continue; $generatedCode .= $generated;` – DaveRandom Oct 27 '11 at 14:59
@DaveRandom Because that is even uglier. You could make it slightly less ugly by negating your condition and having an empty loop body, instead of a while loop containing a single `continue;` statement, which is evil. Poor abused while loop :( – user229044 Oct 27 '11 at 15:02

Randomly generating a character?

5 Answers5