Wordpress - Check if post exists,if yes update fields - wordpress

Question

I use a frontend form to post, and what i want is to check if a post exists by title.If yes and metafield value is bigger than the old one,just replace the value.
Anyone that has implemented something like that in the past?
<?php
session_start();
$user_email = $_SESSION['user_email'];
$user_name = $_SESSION['user_name'];
$user_img_url = 'https://graph.facebook.com/'.$user_name.'/picture?width=200&height=200';
global $wpdb;
global $post;
$title = $user_name; // get the inputted title
$content = $_POST['content']; // get the inputted content
$categorie = $_POST['cat']; // get the category selected by user
$zombies = $_POST['zombies'];
$kliks = $_POST['klik'];
$timess = $_POST['times'];
$name = $_POST['namn'];
if( 'POST' == $_SERVER['REQUEST_METHOD'] ) { // if form has been submitted
$my_post = array(
'post_title' => $title,
'post_content' => $content,
'post_status' => 'publish',
'post_author' => 2,
'post_category' => array(2),
);
$my_post = wp_insert_post($my_post);
add_post_meta($my_post, 'Zombies', $zombies);
add_post_meta($my_post, 'klik', $kliks);
add_post_meta($my_post, 'times', $timess);
add_post_meta($my_post, 'namn', $name);
add_post_meta($my_post, 'profile_photo', $user_img_url);
wp_redirect( home_url() );
# if $verifica is not empty, then we don't insert the post and we display a message
}
?>

Answer 1

Your question is not quite clear to me but if you want to query a post by it's title then you can use get_page_by_title() function as given below
$post = get_page_by_title( $_POST['post_title'], OBJECT, 'post' );
To get a custom meta field you can use get_post_meta() function as given below
$meta_value = get_post_meta($post->ID, 'field_name', true);
Then compare and update the meta value you can use, for example,
if( $_POST['custom_meta_field'] > $meta_value )
{
// Update the meta value
update_post_meta( $post->id, 'field_name', $meta_value );
}
The update_post_meta() function is being used to update the custom meta field.
Update: (Based on comment)
You can use following to get the post that is available by Facebook ID
$post = get_page_by_title( $_POST['facebook_id'], OBJECT, 'post' );
Also if the meta field is time string (12:10 am) then you have to convert it to timestamp/numeric value before you compare it, like,
$meta_value = strtotime(get_post_meta($post->ID, 'field_name', true));
So, it'll become something like 1363493400 and you can compare like
if( $_POST['custom_meta_field'] > $meta_value ){ ... }
In this case your custom_meta_field should be also a timestamp/numeric value or you have to convert it using strtotime() function just like $meta_value has been converted.