PHP Generate random unique password

this function allow you to generate random characters code,function suitable for

Generate activation code for newly user account

Generate shortenURL code,

Generate temporary user password for changing password of account.

function generate_special_pass($pass_len = 8, $allow_special_chrs = true) {
	$allow_chrs = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
	$special_chrs = '!@#$%^&*()_+';
	if($allow_special_chrs) {
		$pass_chrs = $allow_chrs.$special_chrs;
	} else {
		$pass_chrs = $allow_chrs;
	}
	$pass_rand_val = null;
	for($inc =1;$inc<=$pass_len; $inc++ ) {
		$rand_pos = rand(0,strlen($pass_chrs)-1);

		$pass_rand_val .= substr($pass_chrs ,$rand_pos , 1);
	}

	return $pass_rand_val;
}

The 10 is characters limits its generate password with 10 characters and true allow to add special characters these define in $special_vars variable.

echo generate_special_pass(10, true)
//RESULT=Af$@tHiO*q

Now call it as non-special characters with limit of 20

echo generate_special_pass(20, false)
//RESULT=gHoQ0vM5lbX9i1Z70D4B