Question

Hi I’m using foreach to insert into my database multiple authors for a book.

Here is the foreach:

foreach ($_POST["authors"] as $author) 
{
    $sqlAuthor = "INSERT INTO book_author (book_ISBN, author_ID)
        VALUES('$isbn','$author')";

    mysql_query($sqlAuthor);
}

I am getting the authors with a select multiple from my page for which I have created a function to display in the select multiple the authors available.

The code is producing exactly what I want it to produce in the page from my database (the names of all the authors)

Here is the multiple() function:

<?php include ("includes/connections.php");
    function multiple($intIdField, $strfNameField, $strlNameField, $strTableName, $strOrderField, $strNameOrdinal, $strMethod="asc") {
       echo "<select multiple=\"multiple\" name=\"$strNameOrdinal\[\]\">\n";

       $strQuery = "select $intIdField, $strfNameField, $strlNameField
                   from $strTableName
                   order by $strOrderField $strMethod";

       $rsrcResult = mysql_query($strQuery);

       while($arrayRow = mysql_fetch_assoc($rsrcResult)) {
          $strA = $arrayRow["$intIdField"];
          $strB = $arrayRow["$strlNameField"] . " " . $arrayRow["$strfNameField"];    
          echo "<option value=\"$strA \">$strB</option>\n";
       }

       echo "</select>";
    }
?>

Now for some reason it throws the following errors:

Notice: Undefined index: authors in C:\xampp\htdocs\ex\addBook.php on line 63

Warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\ex\addBook.php on line 63

I think it tells me that it can’t find the authors array but I find it very strange

Here the php code inside the html to call the multiple() function:

<?php multiple("author_ID", "author_firstname", "author_lastname", "author", "author_lastname", "authors"); ?>

Anyone has any idea what is wrong with my code?

Answer 1

Every time you use foreach nest it in an if:

if (count($_POST["authors"])) {
    foreach ($_POST["authors"] as $author)  {
       ...
    }
}

so if you have 0 element in the array, or it’s not an array (string, null, anything else) you won’t enter the if, and won’t get the error on foreach’s wrong parameter