[En Español: https://josemmsimo.wordpress.com/2013/01/18/obteniendo-una-cadena-alfanumerica-usando-php]
In this post, I write how is possible generate an aleatory code (with numbers, letters and symbols) using PHP, easy peasy :-) My company ask me this one, for a specific task, and I think that this one could be useful for generate passwords aleatory:
function getRandomCode(){
$an = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-)(.:,;";
$su = strlen($an) - 1;
return substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1);
}
This php code generate 6 aleatory digits. For this one, use:
- rand(X, Y) function: X is the number more small to generate and Y the number more big. With this one, we will have an aleatory number.
- substr(X, Y, Z) function: X is the string, Y is where start the string, and Z is the number of letters. With this one, we will have one digit
- strlen(X) function: X is a string. With this one, we will have the length of the string.
We could be call 100 times to this function so:
for ($i = 0; $i < 100; $i++) echo getRandomCode() . "<br />";
And with a result similar to:
CSHY7S
SGYVAQ
YVU(W7
3MYKSW
WF0FWK
DOP1MU
IO-H3S …
joseMMsimo 
Hello ! This is an old post but it’s still useful for persons like me who’s cannot code themeselves, but can trick a little piece of code for their purpose.
For my html form, I want to auto-generate a random 5 alphanumeric code starting with 2 letters and 3 numbers that will prepopulate a text field when my form loads. Can you help me to achieve this ? I’ve googled but found nothing about auto-filling a form field with an ordonned random string.
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Hello Serge,
I don’t understand very good your idea.
If you want generate 5 alphanumeric code, call to the function 5 times:
for ($i = 0; $i < 100; $i++)
echo getRandomCode() . "
«;
And if you want that the code starts always with 3 specific numbers or 2 specific letters (for example 6, 7, 8, A, B), you could create other string of possibilites:
function getRandomCode(){
$intro = «678AB»;
$an = «0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ»;
$su = strlen($an) – 1;
return substr($intro, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1) .
substr($an, rand(0, $su), 1);
}
So, you could have:
7KJQ2U
AA24ED
B2KJS5
…
:)
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Thanks Jose for your prompt answer.
I’ll be more illustrative. I need to ramdomly generate strings like the below that will auto-populate a form field on page load :
(2 random letters followed by 3 random numbers)
– FG7895
– DE451
– TY321
– ZK952
-…
For now, I found a javascript function that was easy for me to understand and use. It can generate the 5 digits random strings and display them in my field, but they are not syntaxed the way I need, i.e, 2 letters followed by 3 numbers. Please find the script I tested (found on google)
————
function randomString() {
var chars = «123456789ABCDEFGHIJKLMNOPQRSTUVWXTZ»;
var string_length = 5;
var randomstring = »;
for (var i=0; i<string_length; i++) {
var rnum = Math.floor(Math.random() * chars.length);
randomstring += chars.substring(rnum,rnum+1);
}
document.formElem.NameOfMyFormField.value = randomstring;
}
—————-
And I added in the page body tag :
————-
Thank you for your help, Jose
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Hi again,
Well, you need know that JavaScript is not the same that PHP: PHP is running in the server and JavaScript in the browser of the final client. So, the sintax is a bit different. A simple example for JavaScript of this code is this:
<!–
function randomString() {
var letters = "ABCDEFGHIJKLMNOPQRSTUVWXTZ";
var numbers = "123456789";
var numLetters = 2;
var numNumbers = 3;
var randomstring = "";
for (var i=0; i<numLetters; i++) {
var rnum = Math.floor(Math.random() * letters.length);
randomstring += letters.substring(rnum, rnum+1);
}
for (var i=0; i<numNumbers; i++) {
rnum = Math.floor(Math.random() * numbers.length);
randomstring += numbers.substring(rnum, rnum+1);
}
return randomstring;
}
function timesForCall(times) {
var completeText = "";
for (var i=0; i < times; i++) {
completeText += randomString() + "
«;
}
return completeText;
}
document.body.innerHTML = timesForCall(10);
//–>
If you have some question I can try to resolve it :)
I recommend this page for practice code: http://www.codecademy.com/
Enjoy the code!
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