Get variable from PHP to JavaScript

You can print the PHP variable into your javascript while your page is created.

<script type="text/javascript">
    var MyJSStringVar = "<?php Print($MyPHPStringVar); ?>";
    var MyJSNumVar = <?php Print($MyPHPNumVar); ?>;
</script>

Of course this is for simple variables and not objects.

I think the easiest route is to include the jQuery javascript library in your webpages, then use JSON as format to pass data between the two.

In your HTML pages, you can request data from the PHP scripts like this:

$.getJSON('http://foo/bar.php', {'num1': 12, 'num2': 27}, function(e) {
    alert('Result from PHP: ' + e.result);
});

In bar.php you can do this:

$num1 = $_GET['num1'];
$num2 = $_GET['num2'];
echo json_encode(array("result" => $num1 * $num2));

This is what's usually called AJAX, and it is useful to give web pages a more dynamic and desktop-like feel (you don't have to refresh the entire page to communicate with PHP).

Other techniques are simpler. As others have suggested, you can simply generate the variable data from your PHP script:

$foo = 123;
echo "<script type=\"text/javascript\">\n";
echo "var foo = ${foo};\n";
echo "alert('value is:' + foo);\n";
echo "</script>\n";

Most web pages nowadays use a combination of the two.

It depends on what type of PHP variable you want to use in Javascript. For example, entire PHP objects with class methods cannot be used in Javascript. You can, however, use the built-in PHP JSON (JavaScript Object Notation) functions to convert simple PHP variables into JSON representations. For more information, please read the following links:

• PHP JSON Manual
• PHP json_encode function
• PHP json_decode function

You can generate the JSON representation of your PHP variable and then print it into your Javascript code when the page loads. For example:

<script type="text/javascript">
  var foo = <?php echo json_encode($bar); ?>;
</script>

You can pass PHP Variables to your JavaScript by generating it with PHP:

<?php
$someVar = 1;
?>

<script type="text/javascript">
    var javaScriptVar = "<?php echo $someVar; ?>";
</script>

Sure, there are ways to get the $_GET object in javascript by passing it directly from php, but there are other ways ;D

I will proceed to explain both.

1) Direct parse by function. This just grabs the url and parses it directly with RegEx

$_GET=function(key,def){
    try{
        return RegExp('[?&;]'+key+'=([^?&#;]*)').exec(location.href)[1]
    }catch(e){
        return def||''
    }
}

Easy peasy, if the query string is ?ducksays=quack&bearsays=growl, then $_GET('ducksays') should return quack and $_GET('bearsays') should return growl

Now you probably instantly notice that the syntax is different as a result of being a function. Instead of $_GET[key], it is $_GET(key). Well, I thought of that :)

Here comes the second method:

2) Object Build by Loop

onload=function(){
    $_GET={}//the lack of 'var' makes this global
    str=location.search.split('&')//not '?', this will be dealt with later
    for(i in str){
        REG=RegExp('([^?&#;]*)=([^?&#;]*)').exec(str[i])
        $_GET[REG[1]]=REG[2]
    }
}

Behold! $_GET is now an object containing an index of every object in the url, so now this is possible:

$_GET['ducksays']//returns 'quack'

AND this is possible

for(i in $_GET){
    document.write(i+': '+$_GET[i]+'<hr>')
}

This is definitely not possible with the function.

I hope this was helpful and interesting