如何使jQuery / Javascript在PHP语句中工作？

Question

I'm having some difficulties getting Javascript to execute in a PHP statement if it is possible at all. Below I have the code, if the field 'First' is empty, then the background color of a certain div will be yellow. How can I get this to work properly if it is possible in the first place? Thanks in advance.

if (empty($_POST["First"])) {

    echo '<script type="text/javascript">';
    echo '$("div").css({"background-color":"yellow"});';
    echo '</script>';

} 

Answer 1

check this code. hope it will help you

<div>Content Div</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<?php
 //$_POST["First"] = ''; if you want to check this code execute then remove comment then run this code
 if (empty($_POST["First"])) {
echo '<script type="text/javascript">';
echo '$("div").css("background-color","yellow");';
echo '</script>';
}
?>

you can also use this code

<div>Content Div</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<?php
//$_POST["First"] = ''; this is for test case if you want to check then remove comment then run this code
 if (empty($_POST["First"])) { ?>
<script type="text/javascript">
$("div").css("background-color","yellow");
</script>
<?php } ?>

in this code php tag and javascript tag use separate