当我使用php提交表单时，如何从清空中停止勾选框输入？

Question

I'm using the following code for a series of check-boxes.
How can I change the code to prevent the checkboxes from emptying when user submits the form.

    <?php
$services = array(
    'Tree Felling',
    'Height Reduction',
    'Crown Thinning',
    'Deadwooding/Ivy Removal',
    'Stump Grinding',
    'Other'
);
foreach ($services as $option) {
?>
 <label><input id="<?= $option ?>" type="checkbox" name="services[]" <?php
    if ($_POST['services'] == $option) {
        echo 'CHECKED';
    }
?> value="<?= $option ?>" /><?= $option ?></label>
<?
}
?>

I tried this - but It didn't work out. Am I on the right lines?

    <?php
$services = array(
    'Tree Felling',
    'Height Reduction',
    'Crown Thinning',
    'Deadwooding/Ivy Removal',
    'Stump Grinding',
    'Other'
);
foreach ($services as $option) {
?>
 <label><input id="<?= $option ?>" type="checkbox" name="services[]" value="<?= $option ?>" /><?= $option ?></label>
<?
}
?>

Answer 1

You need to check to see if $_POST['services'] is available via isset() (basically that the form's been submitted) and check to see if that service is in the array using in_array(). This worked for me:

<?php
$services = array(
'Tree Felling',
'Height Reduction',
'Crown Thinning',
'Deadwooding/Ivy Removal',
'Stump Grinding',
'Other'
);
foreach ($services as $option) {
?>
<label><input id="<?= $option ?>" type="checkbox" name="services[]" <?php
    if ( isset($_POST['services']) and in_array($option, $_POST['services']) ) {
    echo 'CHECKED';
    }
?> value="<?= $option ?>" /><?= $option ?></label>
<?
}
?>