Undefined index error in custom post metabox - wordpress

Question

I'm getting this error with my custom post metabox. The custom post and metabox works fine, but if I have debug on and when I try to save any other page or post, I will get an error:
Notice: Undefined index: iam_video_select in C:\xampp\htdocs\Iam\wp-content\themes\Iam\inc\classes\Custom_Meta_Boxes.class.php on line 149
Notice: Undefined index: iam_video_url in C:\xampp\htdocs\Iam\wp-content\themes\Iam\inc\classes\Custom_Meta_Boxes.class.php on line 149
Notice: Undefined index: iam_link in C:\xampp\htdocs\Iam\wp-content\themes\Iam\inc\classes\Custom_Meta_Boxes.class.php on line 149
My code:
<?php
$meta_boxes = array();
//Video meta box
$meta_boxes[] = array(
'id' => 'video-meta-box',
'title' => __( 'Video', 'iamtheme' ),
'pages' => 'post',
'context' => 'normal',
'priority' => 'high',
'fields' => array(
array(
'name' => 'Select Video Host',
'id' => PTHEME . '_video_select',
'type' => 'select',
'options' => array( 'Youtube', 'Vimeo', 'Self hosted' )
),
array(
'name' => 'URL',
'desc' => 'Enter video url here.',
'id' => PTHEME . '_video_url',
'std' => 'Default value here.',
'type' => 'text'
)
)
);
//Link meta box
$meta_boxes[] = array(
'id' => 'link-meta-box',
'title' => __( 'Link', 'iamtheme' ),
'pages' => 'post',
'context' => 'normal',
'priority' => 'high',
'fields' => array(
array(
'name' => 'Link',
'desc' => 'Enter your url here.',
'id' => PTHEME . '_link',
'std' => 'Default value here.',
'type' => 'text'
)
)
);
/**
*
*/
class Custom_Meta_Boxes{
public $_meta_box;
public function __construct( $meta_box ){
$this->_meta_box = $meta_box;
add_action( 'add_meta_boxes', array( $this, 'iam_add_meta_box' ) );
add_action( 'save_post', array( $this, 'iam_save_meta_box_data' ) );
}
/**
* Adds a meta box to the post editing screen
*/
public function iam_add_meta_box(){
add_meta_box(
$this->_meta_box['id'],
$this->_meta_box['title'],
array( &$this, 'iam_display_custom_meta_box' ),
$this->_meta_box['pages'],
$this->_meta_box['context'],
$this->_meta_box['priority']
);
}
/**
* Render Meta Box content.
*/
public function iam_display_custom_meta_box() {
global $post;
// Add an nonce field so we can check for it later.
wp_nonce_field( 'iam_nonce_check', 'iam_nonce_check_value' );
echo '<div class="metabox-wrapper">';
foreach ( $this->_meta_box['fields'] as $field) {
// get current post meta data
$meta = get_post_meta( $post->ID, $field['id'], true );
echo '<div class="metabox-fields metabox_' , $field['type'] , '">';
echo '<label for="', $field['id'] , '">', $field['name'] , '</label>';
switch ( $field['type'] ) {
case 'text':
echo '<input type="text" name="', $field['id'] , '" id="', $field['id'] , '" value="', $meta , '" />';
echo '<p class="meta-desc">' , $field['desc'] , '</p>';
break;
case 'textarea':
echo '<textarea name="', $field['id'], '" id="', $field['id'], '" cols="60" rows="4" style="width:97%">', $meta , '</textarea>';
echo '<p class="meta-desc">' , $field['desc'] , '</p>';
break;
case 'select':
echo '<select name="', $field['id'], '" id="', $field['id'], '">';
foreach ( $field['options'] as $option ) {
echo '<option', $meta == $option ? ' selected="selected"' : '', '>', $option, '</option>';
}
echo '</select>';
break;
case 'radio':
foreach ( $field['options'] as $option ) {
echo '<input type="radio" name="', $field['id'], '" value="', $option['value'], '"', $meta == $option['value'] ? ' checked="checked"' : '', ' />', $option['name'];
}
break;
case 'checkbox':
echo '<input type="checkbox" name="', $field['id'], '" id="', $field['id'], '"', $meta ? ' checked="checked"' : '', ' />';
break;
}
echo '</div>';
}
echo '</div>';
}
/**
* Save the meta when the post is saved.
*/
public function iam_save_meta_box_data( $post_id ){
if( $this->iam_user_can_save( $post_id, 'iam_nonce_check_value' ) ) {
// Checks for input and sanitizes/saves if needed
foreach ( $this->_meta_box['fields'] as $field ) {
$old = get_post_meta( $post_id, $field['id'], true );
$new = sanitize_text_field( $_POST[ $field['id'] ] );
if ( $new && $new != $old ) {
update_post_meta( $post_id, $field['id'], $new );
} elseif ( '' == $new && $old ) {
delete_post_meta( $post_id, $field['id'], $old );
}
}
}
}
/**
* Determines whether or not the current user has the ability to save meta
* data associated with this post.
*
* #param int $post_id The ID of the post being save
* #param bool Whether or not the user has the ability to save this post.
*/
public function iam_user_can_save( $post_id, $nonce ){
// Checks save status
$is_autosave = wp_is_post_autosave( $post_id );
$is_revision = wp_is_post_revision( $post_id );
$is_valid_nonce = ( isset( $_POST[ $nonce ] ) && wp_verify_nonce( $_POST[ $nonce ], 'iam_nonce_check' ) ) ? 'true' : 'false';
// Return true if the user is able to save; otherwise, false.
return ! ( $is_autosave || $is_revision ) && $is_valid_nonce;
}
}
// Instantiate theme
if ( class_exists( 'Custom_Meta_Boxes' ) ){
foreach ( $meta_boxes as $meta_box ) {
$my_box = new Custom_Meta_Boxes( $meta_box );
}
}
?>
Thanks for any helps.