使用可变数量的变量在PDO / SQL中更新:)

Question

I have a code that retrieves all the input data sent in a form. If the form had only 2 fields filled out, the PHP gets the value for only those 2 fields (the unchanged fields in the form are not submitted).

Then I would like to UPDATE a SQL table for those fields that I have retrieved with my PHP code. Here is where I am lost. I would need to specify in the SQL only the fields that I have received from the form, but this is variable. Maybe I received only 1 field, maybe I received 7 of the fields...

Here is my code:

if (isset($_POST) && !empty($_POST))  {
echo $internalImage;

foreach ($_POST as $key => $value) 
    {
 echo "Field Name: ".htmlspecialchars($key)." | Value: ".htmlspecialchars($value)."<br>";
    }
}

What would you suggest?

Answer 1

You could construct your query like this:

$values=array();

//this will be an array of possible fields that are in your table
$possible=array('field1', 'field2', 'field3');

$i=0;
$len=count($_POST);
$query='update table_name set ';
foreach($_POST as $key => $value){
  $k=htmlspecialchars($key);
  $v=htmlspecialchars($value);
  if(in_array($k, $possible)){
    $query .= $k .' = ?'; //placeholder for a value
    $values[]=$v;  //append values to an array for later use
    if($i < ($len-1)) $query .= ', ';
    $i++;
  }
}
$query .= 'where table_id = ?';
$values[]=$table_id; //forgot that, append id of a row you are to update.

and then prepare and execute the query:

$db->prepare($query);
$db->execute($query, $values);