<?php
/**
 * Function that generates a string with random caracters.
 * 
 * $length: The length of the random string. 
 * 
 * $randomCase: If true, the generated string will also include uppercase alphabet caracters randomly.
 * 
 * $includeDigits: If true, the generated string will also include digits randomly.
 */
function random_chars($length = 10, $randomCase = false, $includeDigits = false)
{
	$lower = 'abcdefghjkmnpqrstuvwxyz';
	$upper = 'ABCDEFGHJKMNPQRSTUVWXYZ';
	$digits = '0123456789';
	$chars = $lower . ($randomCase ? $upper : '') . ($includeDigits ? $digits : '');
	$str = '';
 
	$last_index = strlen($chars) - 1;
	for($i = 0; $i < $length; $i++)
	{
		mt_srand(hexdec(uniqid()));
		$str .= $chars[mt_rand(0, $last_index)];
	}
	return $str;
}
 
//How to use
$length = 20;//The string length
//$random_lower: random lowercase alphabet chars, something like: rswcjanzybtaxranszxm
$random_lower = random_chars($length);
//$random_case: random lowercase and uppercase alphabet chars, something like: kTjkvrrejtuArxpNcPJR
$random_case = random_chars($length, true);
//$random_chars_digits: random lowercase and uppercase alphabet chars plus digits, something like: 9GY5KY8Q4wZ81Ge5UvDK
$random_chars_digits = random_chars($length, true, true);
 
echo $random_lower . '<br />';
echo $random_case . '<br />';
echo $random_chars_digits;
?>