Fill jQuery or ajax by PHP var - php

Question

Is it possible to fill jQuery variable by PHP???
I mean something like this:
<?php
$string_php = "50%";
?>
And with "$string" variable I want to fill jQuery:
var jquery_string = "$string_php";
$('.bar1').animate({'height':'jquery_string'},500);
The code above is only idea how I would like to be working

Answer 1

Yes but with php tags <?php ?> (so that php knows its code):
var jquery_string = "<?php echo $string_php;?>";
$('.bar1').animate({'height':jquery_string}, 500); // no quotes for variables
It is possible because PHP (server-side) runs before jQuery (client-side). The page first goes to server and server returns the response (php code is parsed there) to the browser.

Answer 2

Sure
var jquery_string = "<?php echo $string_php;?>";
Since PHP is processed first on the server and the result is then sent to the user's browser, this is easy, and often done.
The above code would result in:
var jquery_string = "50%";
You would, however want to modify your second line, removing the quotes from the variable so it was:
$('.bar1').animate({'height':jquery_string},500);
since keeping the quotes around jquery_string would make force it to be interpreted as a string whereas you want a variable.
The end result would be the equivalent of:
$('.bar1').animate({'height':'50%'},500);

Answer 3

For simple variables, just do as the users said.
F.ex. var jquery_string = "<?php echo $string_php;?>"; (taken from #Blaster's solution).
In other words:
The most simple solution is to output a php variable that we intend to use as string literal via echo anywhere we define the variable.
But: a correct approach would be that everytime we use a serverside variable as a Javascript string, it should be encoded, because the above solutions would fail when double quotes are present. Here json_encode may come handy.
var jquery_string = <?php echo json_encode($var); ?>;
Code example
We want Javascript alert the string "Hey", dude!
$string = "\"Hey\", dude!";
echo "alert(\"" . $string . "\");";
results in:
alert(""Hey", dude!"); <--- will give Javascript error
Instead:
echo "alert(" . json_encode($string) . ");";
results in:
alert("\"Hey\", dude!"); <---- correct JS code