Can't access array via $_POST - php

Question

I have the following html code:
<form method="post" action="arrayplay.php">
<input type="checkbox" value="1" name="todelete[]"/>
<input type="checkbox" value="2" name="todelete[]"/>
<input type="checkbox" value="3" name="todelete[]"/>
<input type="checkbox" value="4" name="todelete[]"/>
<input type="submit" value="delete" name="delete"/>
</form>
And the following PHP script:
//arrayplay.php
foreach ($_POST['todelete'] as $id)
{
echo $id . "<br/>";
}
?>
It is supposed to echo out each element value but instead I get an error. I am getting really frustrated. If I use:
<form method="post" action="arrayplay.php">
<?php
$dbc= //connection
$query = "SELECT * FROM email_list";
$result = mysqli_query($dbc, $query);
while ($row = mysqli_fetch_array($result)) {
echo '<input type="checkbox" value="' . $row['id'] . '" name="todelete[]" />';
echo $row['first_name'];
echo ' ' . $row['last_name'];
echo ' ' . $row['email'];
echo '<br />';
}
mysqli_close($dbc);
?>
<input type="submit" name="submit" value="Remove" />
</form>
It works perfectly fine! Why? The first (hard coded html) holds the exact same value as the one that retrieves them from the database. I am having a real hard time understanding retrieving values from an array with $_POST. Why does name=foo[] create an array? Is it an associative or numeric array? I'm sorry for all of the questions, I'm just really ready to pull my hair out.

Answer 1

if you just named the input foo it would only get one value. because square brackets are commonly used for arrays, foo[] is how in the html form, you indicate an array. of course on the PHP side you just call it foo as you are aware from your working example.

Answer 2

I've tested this and it should work:
<?php
if ($_POST['delete']) {
foreach ($_POST['todelete'] as $id) {
echo $id.' selected<br />';
}
}
?>
<form method="post" action="arrayplay.php">
<input type="checkbox" value="1" name="todelete[]"/>
<input type="checkbox" value="2" name="todelete[]"/>
<input type="checkbox" value="3" name="todelete[]"/>
<input type="checkbox" value="4" name="todelete[]"/>
<input type="submit" value="delete" name="delete"/>
</form>
If you're still having troubles, you can try:
<?php
if ($_POST['delete']) {
for ($i = 0; $i < 4; $i++) {
if (isset($_POST['todelete'][$i])) {
echo $_POST['todelete'][$i].' selected<br />';
}
}
}
?>