Wordpress update_post_meta does not update dynamic values

This is a little strange, I am using "update_post_meta" to update the custom fields in Wordpress. When I run update_post_meta($post_id, 'Test_Field', 'Test Value'); the custom field updates without a problem BUT when I use a string value it does not update:

$test_value = "Test";
 echo $test_value; // No problem here
 echo $post_id; // No problem here
 update_post_meta($post_id, 'Test_Fiel开发者_如何转开发d', $test_value);

Thanks very much in advance for your help

Stu

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Try to cast variables with types. Try this:

update_post_meta( (int) $post_id, 'Test_Field', (string) $test_value );

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Your first example used $post_id and solution $page_id. Was that a typo?

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It might sound strange but, meta_key name must be identical to the input field name.

update_post_meta( $post_id, 'top_image', $_POST['top_image'] );