<?php
add_filter('acf/location/rule_types', 'acf_location_rules_types');
function acf_location_rules_types( $choices ) {
	
    $choices['Utilisateur']['user_id'] = 'ID utilisateur';
    return $choices;
	
}

add_filter('acf/location/rule_values/user_id', 'acf_location_rules_values_user');
function acf_location_rules_values_user( $choices ) {
	
    $choices[ 511 ] = 'ADMIN 2018 (511)';
    return $choices;
    
}

add_filter('acf/location/rule_match/user_id', 'acf_location_rules_match_user', 10, 3);
function acf_location_rules_match_user( $match, $rule, $options )
{
	
    $selected_user = (int) $rule['value'];
    
    if($rule['operator'] == "==") {
    	$match = ( wp_get_current_user()->ID == $selected_user );
    }
    elseif($rule['operator'] == "!=") {
    	$match = ( wp_get_current_user()->ID != $selected_user );
    }
    
    return $match;
    
}