CODEWITHSUNDEEP
phpgenerator
forgatn
forgatn

Reputation: 279

Generator for random long hex strings in PHP

I have written a generator of strings, but I don't know how to create a random hex string with length, for instance 100 digits, for inserting into a database. All these strings have to be same length.

How can I generate random hex strings?

Upvotes: 18

Views: 25057

Answers (6)

Bernhard D
Bernhard D

Reputation: 61

From php7 on you should use the function random_bytes:

function getRandomHex($num_bytes=4) {
  return bin2hex(random_bytes($num_bytes));
}

Upvotes: 5

Marcin Orlowski
Marcin Orlowski

Reputation: 75629

While this answers OP's question, if what you are looking for is random, then @danorton answer may be a better fit.

Like this:

$val = '';
for( $i=0; $i<100; $i++ ) {
   $val .= chr(rand(65, 90));
}

65 is A while 90 is Z. if you do not like "magic numbers" this form may be more readable:

$val = '';
for( $i=0; $i<100; $i++ ) {
   $val .= chr(rand(ord('A'), ord('Z')));
}

I'd make ord() result a variable and move it out of the loop though for performance reasons:

$A = ord('A');
$Z = ord('Z');
$val = '';
for( $i=0; $i<100; $i++ ) {
   $val .= chr(rand($A, $Z));
}

Or you could glue output of sha1()s (three of them) and cut down to 100 chars. Or use md5() instead (but I'd stick to sha1()).

EDIT sha1() outputs 40 chars long string, md5() 32 chars long. So if you do not want to glue char by char (as in loop I gave above) try this function

function getId($val_length) {
    $result = '';
    $module_length = 40;   // we use sha1, so module is 40 chars
    $steps = round(($val_length/$module_length) + 0.5);

    for( $i=0; $i<$steps; $i++ ) {
      $result .= sha1(uniqid() . md5(rand());
    }

    return substr($result, 0, $val_length);
}

where function argument is length of string to be returned. Call it getId(100);

Upvotes: 7

Sabo
Sabo

Reputation: 1677

I like to a have single general function that can handle similar situations. By that I mean a function which receives both the requried length of the generated string and the possible characters that can occure in it.

That way a single function can create: 40-digit decimal number, 16-digit uppercase hex number, 100 letter lowercase string, etc...

Here is my implementation:

/**
 * Generate a random string.
 *
 * @param int    $length Length of the generated string.
 * @param string $chars  The string containing all of the available characters.
 *
 * @return string The generated string.
 */
function getRandomString($length = 10, $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789') {
    $str = '';

    $size = strlen($chars);
    for ($i = 0; $i < $length; $i++) {
        $str .= $chars[mt_rand(0, $size - 1)];
    }

    return $str;
}

IMPORTANT: Do not use this function to generate random string for any security purpose. For a secure string generator check out the answer from @danorton.

Upvotes: 0

danorton
danorton

Reputation: 12015

As of PHP 5.3 with OpenSSL extension:

function getRandomHex($num_bytes=4) {
  return bin2hex(openssl_random_pseudo_bytes($num_bytes));
}

For your example of 100 digits:

$str = getRandomHex(50);

Upvotes: 44

Dmitriy Sintsov
Dmitriy Sintsov

Reputation: 4159

$randHexStr = implode( array_map( function() { return dechex( mt_rand( 0, 15 ) ); }, array_fill( 0, $strlen, null ) ) );

where $strlen is length of random hex string.

Upvotes: 5

Yash Savalia
Yash Savalia

Reputation: 11

liner technique to do so, but its bit complicated and hard-coded in-terms of length of string.

$rand4 = substr(sha1(rand(0,getrandmax())),rand(0,24),16);

in which you need to change the last varibale of function (which i set to 16) if you want to change the length of output string and one more thing there is one rand(0,24) in which number 24 will change according to third variable, it should not be more then 40-thirdvariable...

Upvotes: 1

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