Sanitize callback for WordPress register_meta() function.

functions.php

<?php //* do not include php tag

/**
 * Callback for WordPress register_meta() sanitize parameter.
 *
 * Sanitize the 'sample_count' meta value before saved to the database.
 *
 * @see https://codex.wordpress.org/Function_Reference/register_meta
 * 
 * @uses absint()
 * @see https://codex.wordpress.org/Function_Reference/absint
 * 
 * @param  mixed  $meta_value The meta value.
 * @param  string $meta_key   The meta key.
 * @param  string $meta_type  The meta type.
 * @return mixed              The meta value.
 */
function sanitize_sample_count_meta( $meta_value, $meta_key, $meta_type ) {
    
    return absint( $meta_value );
    
}