PHP Function Not Running Correctly

Question

<?php

function pass($level=2,$length=6) {

    $chars[1] = "023456789abcdefghijmnopqrstuvwxyz";
    $chars[2] = "23456789abcdefghijmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";

    $i = 0;
    $str = "";

    while ($i<=$length) {
        $str .= $chars[$level][mt_rand(0,strlen($chars[$level]))];
        $i++;
    }

    return $str;

}

echo pass(2, 7);

?>

When I call the function, I really can't set anything up. pass(2,7) is the same length as pass(1, 9). It's all level 2 and some length. What's wrong?

Where are you declaring that $chars is an array?

Chris Eberle
– Chris Eberle

2011-07-11 18:29:08 +00:00
Commented Jul 11, 2011 at 18:29 — Chris Eberle
– Chris Eberle, Commented Jul 11, 2011 at 18:29
os-code-web.blogspot.com/2011/04/…

Jagan Chennai
– Jagan Chennai

2011-07-11 18:29:32 +00:00
Commented Jul 11, 2011 at 18:29 — Jagan Chennai
– Jagan Chennai, Commented Jul 11, 2011 at 18:29

rockerest · Accepted Answer · 2011-07-11 18:44:21Z

1

The other answers seem to ignore the fact that strings are treated as arrays of characters in php (see the section String access and modification by character).

Your script worked fine for me with two modifications:

First:

You are referencing a character randomly from 0 to the length of the string. This doesn't work, string arrays are 0-indexed, and therefore 1 less than the length.

Try:

$str .= $chars[$level][mt_rand(0,strlen($chars[$level]) - 1)];

Second:

You are looping through this procedure from 0 to the length specified, meaning that it will loop $length + 1 times.

Try:

while ($i < $length) {

this worked perfectly for me.

Here's sample output:

print pass(2, 7) //prints IR5YgGD
print pass(1, 10) //prints d2eyq547gy

answered Jul 11, 2011 at 18:44

rockerest

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1 Comment

blitzmann Over a year ago

Basically what I tried to do, but you've actually explained why it is the way it is. Kudos ^_^

Patrick Desjardins · Accepted Answer · 2011-07-11 18:48:23Z

1

You need -1 to not overflow.

You can use substr to [] to access.

function pass($level=1,$length=6) {

$chars = array();
$chars[0] = "023456789abcdefghijmnopqrstuvwxyz";
$chars[1] = "23456789abcdefghijmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";

$i = 0;
$str = "";
while ($i<$length) 
{
    $index = mt_rand(0,strlen($chars[$level])-1);//It's inclusive you need -1
    $str .= substr($chars[$level],$index,1);//Take the index with 1 for a single char
    //You can also use:
    //$str .= $chars[$level][$index];
    $i++;
}

return $str;

}

echo pass(0, 7);//Start at 0 because array start at 0. So it's your Level1
echo pass(1, 7);//Start with 1, it's your Level2    
?>

edited Jul 11, 2011 at 18:48

answered Jul 11, 2011 at 18:29

Patrick Desjardins

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11 Comments

blitzmann Over a year ago

Doesn't work for me. If you pass 7 as the length, you can get a result of either 7 or 8 characters

Patrick Desjardins Over a year ago

I do not have a compiler of PHP with me now, I am sure you can from what I have wrote found the little glitch. The main point is to use SUBSTR instead of trying to get char with array.

blitzmann Over a year ago

You can also use {n} to extract the nth character from a string. I think that's what he was trying to do when using []

Patrick Desjardins Over a year ago

It works. Do not forget to pass 1 and 6 now because array start at 0 not 1.

Patrick Desjardins Over a year ago

I tested at : writecodeonline.com/php pass(0,6) pass(1,6) pass(1,7) and all works. Have a nice day.

|

genesis · Accepted Answer · 2011-07-11 18:34:31Z

0

This will work fine

<?php

function pass($level=2,$length=6) {

$chars[1] = array("0","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","m","n","o","p","q","r","s","t","u","v","w","x","y","z");
$chars[2] = array("2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A","B","C","D","E","F","G","H","I","J","K","L","M","N,"P","Q","R",""S","T","U","V","W","X","Y","Z");

$i = 0;
$str = "";
while ($i<=$length) {
    $str .= $chars[$level][mt_rand(0,count($chars[$level])-1)];
    $i++;
    }

return $str;

}

echo pass(2, 7);

?>

answered Jul 11, 2011 at 18:34

genesis

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Comments

Mark Bell · Accepted Answer · 2011-07-11 19:49:26Z

0

Here's what I got. I define the length mt_rand() needs, and then use curly braces {} to extract the character at the random index:

function pass($level=2, $length=6) {

    $chars[1] = "023456789abcdefghijmnopqrstuvwxyz";
    $chars[2] = "23456789abcdefghijmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";

    $i = 0;
    $str = "";
    $charLen = strlen($chars[$level]) -1;

    while ($i<$length) {
        $str .= $chars[$level]{mt_rand(0,$charLen)};
        $i++;
    }

    return $str;
}

$result = pass(2, 21);

edited Jul 11, 2011 at 19:49

Mark Bell

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answered Jul 11, 2011 at 18:42

blitzmann

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