Question

All,
I have the following code:

$qry = "Select * from vendor_options order by vendor_option_name ASC";
$result = mysql_query($qry);
while($resultset = mysql_fetch_array($result)){
    if(isset($_SESSION['pav_choosen_vendor_categories'])){
        for($z=0;$z<$_SESSION['pav_choosen_vendor_categories'];$z++){
            $sVendorId = $_SESSION['pav_vendor_categories_' . $z];
                if($sVendorId==$resultset['vendor_option_id']){
                    $vendor_cats_choosen[] = $sVendorId;
                }
        }
        if(in_array($resultset['vendor_option_id'],$vendor_cats_choosen)){
        ?>
        <input type="checkbox" value="<?php echo $resultset['vendor_option_id']; ?>" class="select_vendor" name="vendor_categories[]" checked><?php echo $resultset['vendor_option_name']; ?><br>
            <?php
        }else{
        ?>
        <input type="checkbox" value="<?php echo $resultset['vendor_option_id']; ?>" class="select_vendor" name="vendor_categories[]"><?php echo $resultset['vendor_option_name']; ?><br>
        <?php
        }
    }
}

I’m trying to check to see if the value returned in the mysql_fetch_array is already in my array. Say the first value it finds in the array is in the fourth iteration of the while loop. I’ll get the following error:

Warning: in_array() expects parameter 2 to be array, null

Once it gets to a value that is in the array the rest of them work fine. Why does itgive an error for the first couple? Thanks.

Answer 1

It looks like you have not initialized $vendor_cats_chosen to be an array, and so if the condition if($sVendorId==$resultset['vendor_option_id']) is not true, no elements will be appended to it, turning it implicitly into an array.

Initialize it before the while loop. You should just about always initialize arrays before use.

// Initialize the array
$vendor_cats_chosen = array();
while($resultset = mysql_fetch_array($result)){
  ....

Now, when your in_array() statement executes, the array may be empty, but will be a valid array.

// $vendor_cats_chosen might be an empty array, or may have elements.
if(in_array($resultset['vendor_option_id'],$vendor_cats_choosen)){