How to make jQuery/Javascript work in PHP statement?

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>';
} 

• Loko: Is there a reason you're not doing this check in javascript instead of PHP?
• Lord Goderick: No particular reason, I was just wondering if it is possible and if so, how to achieve it.
• Reinstate Monica Cellio: Consider adding a class to the div in PHP, and then having that class in CSS to set the background colour.
• Antonios Tsimourtos: Also, something that it is going to really help you is to use like that <?php if (empty($_POST["First"])) { ?> <script type="text/javascript"> $("div").css({"background-color":"yellow"}); </script> <?php } ?>
• mplungjan: What is the difficulty? It looks correct assuming you have loaded jQuery before the statement. Any console errors?

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

Answer 2

You should try putting script tags inside php tags, like this:

<?php 
 if (empty($_POST["First"])) { ?>
 <script type="text/javascript">
 '$("div").css({"background-color":"yellow"});';
 </script>
<?php } ?>

Here is an example: https://stackoverflow.com/a/13254287/7808973