php - PDO update only updating one row -

so quite confused problem. sending post php file using ajax , takes array, reverses it, chunks , uses bind values. each chunk holds row worth of info update, each iteration of loop updates row.

the first time attempted used following code.

if(isset($_post['saveedits'])) {     $i = 0;     $j = 1;      $update = array();               $update = $_post['saveedits'];     $chunk_count = count($update)/7;         $backwards = array_reverse($update);     $chunks = array_chunk($backwards, 7);                     try {         for($i; $i < $chunk_count; $i++ ) {             $update_project = $db->prepare('                 update projects                 set comments = ?,                     contact = ?,                     est_end = ?,                     est_start = ?,                       apm = ?,                       pm = ?                                               id = ?             ');              foreach ($chunks[$i] $field => $val) {                                            $update_project->bindvalue($j++, $val, pdo::param_str);                                              }                        $update_project->execute();          }          echo 'projects updated';              } catch(pdoexception $e) {         die($e->getmessage());     }    } else {         echo 'could not update projects table'; } 

and following error each time

warning: pdostatement::execute(): sqlstate[hy093]: invalid parameter number: parameter not defined in c:\xampp\htdocs\core\functions\update_projects.php on line 31 

so suggested change

$i = 0; 

to

$i = 1; 

this somehow works. lets me insert data 1 time, not insert of data. fact works at all baffling me. $i holder loop index, , chunks index. needs go 0 - whatever. don't understand how starting @ 1 helps in way. $j holder param binder, should start @ 1.

some additional info. if var_dump(chunks[0]) , var_dump(chunks[1]) see following

array(7) { [0]=> string(13) "more comments" [1]=> string(9) "jimmy doe" [2]=> string(6) "1-1-14" [3]=> string(7) "12-1-13" [4]=> string(9) "janey doe" [5]=> string(9) "jonny doe" [6]=> string(2) "17" }  array(7) { [0]=> string(13) "some comments" [1]=> string(7) "jim doe" [2]=> string(6) "1-1-14" [3]=> string(7) "12-1-13" [4]=> string(8) "jane doe" [5]=> string(7) "jon doe" [6]=> string(2) "16" } 

so review. $i = 0 , error top, $i = 1 insert 1 row , it's over. can please tell me what's going on here? appreciated

there multiple problems code. main issue though way attempting split array chunks. let's have 10 items in array, given code $chunk_count = count($update)/7;, give chunk count of 1.4285..., greater 1, less 2. in loop, expect run once if $i = 1; because first time through loop, 1 < 1.x, second time 2 > 1.x.

what trying accomplish breaking array? process straight through. remember keep simple when possible.