得到php布尔值并改变css边框颜色取决于它？

php

public function livecheck($check_value, $value){
    global $connection;

    $query = "SELECT * FROM users WHERE $check_value = ? LIMIT 1";
    $results = $connection->select($query,$value);

    //return total count
    $results_exist = $results->rowCount();
    $results_exist = $results->fetch();

    //if value is more than 0, username is not available
    if($results_exist) {
        //out jquery echo
        echo "We're sorry, that username is not available.";
        //return fail change border to red
        $_exist = true;
    }else{
        echo "username is available.";
        //return true change border to grey
        $_exist = false;
    }
}

jquery

function checkusername(){
        var username_value = $("#username").val();

            if (username_value.length >= 4){
            //checking the database username exits
            // $("#user-result").html('<img src="imgs/ajax-loader.gif" />');
            // post value isit using it self?//
            $.post('class/validation.php', {'username':username_value}, function(data) {
            $("#user-result").html(data);
            // get the return data from php , fail = red , true = grey
            $("#username").css(data);
            });
        }
        return;
    }

this is a live validation checking my database username and my intention is use jquery to change my css border color depends on my php return Boolean , i was able to echo the Boolean data ,so php check if username exists , border = red , else border = grey.

i hope i explain it right , i cant figure it out where to start this.

Don't just send the message from PHP. Send JSON object. And depending on the value of exists inside object change the colour of the textbox.

PHP:

public function livecheck($check_value, $value){
    global $connection;

    $query = "SELECT * FROM users WHERE $check_value = ? LIMIT 1";
    $results = $connection->select($query,$value);

    //return total count
    $results_exist = $results->rowCount();
    $results_exist = $results->fetch();

    //if value is more than 0, username is not available
    if($results_exist) {
        //out jquery echo
        $response = array(
            "message"=> "We're sorry, that username is not available.",
            "exist"=> true
        );
        // ^^^^^^^^^^^^^^
    } else {
        $response = array(
            "message"=> "username is available.",
            "exist"=> false
        );
        // ^^^^^^^^^^^^^^
    }
    echo json_encode($response);
}

Javascript:

function checkusername() {
    var username_value = $("#username").val();

    if (username_value.length >= 4) {
        //checking the database username exits
        // $("#user-result").html('<img src="imgs/ajax-loader.gif" />');
        // post value isit using it self?//
        $.post('class/validation.php', {
            'username': username_value
        }, function (data) {
            var usernameAvailable = JSON.parse(data);
            $("#user-result").html(usernameAvailable.message);

            var color = usernameAvailable.exist ? 'gray' : 'red';

            $("#username").css('border-color', color);
        });
    }
    return;
}

So you get the either the values red or grey returned? In that case you should set the css in the following way:

$("#username").css('border-color',data);

You need to return the variable and the text, so you're going to have to use JSON. You need to change this part in your PHP file:

$return = array('text' => '', 'exists' => false);
if($results_exist) {
    //out jquery echo
    //echo "We're sorry, that username is not available.";
    $return['text'] = "We're sorry, that username is not available.";
    //return fail change border to red
    $return['exists'] = true;
}else{
    //echo "username is available.";
    $return['text'] = "username is available.";
    //return true change border to grey
    //$_exist = false;
}
echo json_encode($return);

Then for your JavaScript:

function checkusername(){
    var username_value = $("#username").val();

    if (username_value.length >= 4){
        //checking the database username exits
        // $("#user-result").html('<img src="imgs/ajax-loader.gif" />');
        // post value isit using it self?//
        $.ajax(function() {
            type: 'POST',
            url: 'class/validation.php', 
            data: {'username':username_value}, 
            dataType: 'JSON' //This tells the ajax we're expecting a JSON response.
        })
        .done(function(data) {
            $("#user-result").html(data.text);
            // get the return data from php , fail = red , true = grey
            $("#username").css('border-color', data.exists ? 'grey' : 'red');
        });
    }
    return;
}