Updating a wp_postmeta field not working in wordpress

Question

I cannot update a wp_postmeta field called 'alive_days' and making its value equal to zero, in wordpress. I have tried all the two following solutions but still not working:

1. $alive_days='alive_days';$mypostid=$_REQUEST['pid'];
2. global $wpdb;
3. $wpdb->query("update $wpdb->wp_postmeta set meta_value==\\"$ziro\\" where post_id=\\"$mypostid\\" and meta_key=\\"$alive_days\\"");

1. $ziro=0;
2. $mypostid=$_REQUEST['pid'];
3. update_post_meta($mypostid, 'alive_days',$ziro);

The field value will not change after the execution.

Answer 1

Try This,

 $ziro=0; $alive_days = 'alive_days'; $mypostid = $_REQUEST['pid']; 

global $wpdb;
$wpdb->update( 
    'wp_postmeta', 
    array( 
        'meta_value' => $ziro,  
        'meta_key' => $alive_days   
    ), 
    array( 'ID' => $mypostid )

);

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Answer 2

尝试使用此代码

update_post_meta( $post_id,'alive_days', 0 );