Question

I have a list of checkboxes and save the checked values in an array. However, when someone clicks ‘submit’ and they get an error, all their checked boxes are forgotten. Usually I would let the script remember the checked boxes with a code like

IF checkbox value = OK { echo checked=”checked”}

However, now I save it in an array and I have no idea how to do this?

<?php

$sql = "SELECT merknaam FROM merken";
$result = mysql_query($sql);

while ($row = mysql_fetch_array($result)) {
    echo "&nbsp;&nbsp;<input type=\"checkbox\" name=\"merken[]\" value='" . $row['merknaam'] . "'>&nbsp;" . $row['merknaam'] . " <Br />  ";
}

?>

This is the code I use for the checkboxes. Next I display the array with this code:

$merkenstring = implode(",", $_POST['merken']);

echo $merkenstring;

Result: AC Ryan,Adidas,Agu,Cargo

I hope someone could give me a code example!

Answer 1

Assuming you are posting this to the same page, and $_POST['merken'] is still available after an error, use in_array() to test each checkbox’s value against the current set in $_POST:

while ($row = mysql_fetch_array($result)) {
    // If the current value is in the $_POST['merken'] array
    // and the array has been initialized...
    if (isset($_POST['merken']) && is_array($_POST['merken']) && in_array($row['merknaam'], $_POST['merken'])) {
      // Set the $checked string
      $checked = "checked='checked'";
    }
    // Otherwise $checked is an empty string
    else $checked = "";
    // And incorporate it into your <input> tag
    echo "&nbsp;&nbsp;<input $checked type=\"checkbox\" name=\"merken[]\" value='" . $row['merknaam'] . "'>&nbsp;" . $row['merknaam'] . " <Br />  ";
    //----------------------^^^^^^^^^^
}

If this was posted to a different script, you would (as with any post value returned to a previous script) need to store the array in $_SESSION instead and compare against $_SESSION['merken'] in your in_array() call.