40 points for a small piece of PHP code, everyone, please enter the solution

40 points for a small piece of PHP code, everyone please enter
Demand:
Randomly take a number from the two number of a, B, and make up a string of 10 characters.

Requirements:
1, the adjacent two letters can not be the same (except 0), if randomly taken to the same 2 consecutive letters, you need to convert the following letter to 0, until another different letter, such as the abbb after the result of the cycle, need to convert to ab00;
2. The overlapping letters cannot be processed outside the loop, and this operation needs to be done when the string is generated.

Examples of final and correct results: 0A000B00AB, or ABAB0000BA



Thank you!

------Solution--------------------

PHP Code

$last = '; $r = '; for ($i =0; $i <10; $i + +) {  $t = rand (0, 1) >0.5? ' A ': ' B ';  $r. = $t = = $last? ' 0 ': $t;  $last = $t;} Echo $r;
------Solution--------------------

  
  
function Chkstr ($a, $b)
{
   $str = ";
   $c = ";
   $d = ";
   $arr =array ($a, $b);
   while (strlen ($STR) <10)  
   {
       $d =rand (0,1);
       $str. = ($c = = $arr [$d])? ("0"): ($arr [$d]);  
       $c = ($c = = $arr [$d])? ("0"): ($arr [$d]);     
   }  
   
}

Echo Chkstr (A, b);

?>
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