Use a php variable into javascript

Question

class Map
{
public $Id;
public $longitudes;
public $latitudes;
public $lat_init;
public $lng_init;
public static function createMap($Id){
 global $latitude, $longitude;
 $dbh = Database::connect();
 $query = "SELECT * FROM `cartes` WHERE Id=? ";
 $sth = $dbh->prepare($query);
 $sth->setFetchMode(PDO::FETCH_CLASS, 'Map');
 $sth->execute(array($Id));
 if ($sth->rowCount() === 0) return NULL;
 $map=$sth->fetch();
 $sth->closeCursor();
 $lat=$map->latitudes;
 $lng=$map->longitudes;
 $latitude=unserialize($lat);
 var_dump($latitude);
 $longitude=unserialize($lng);
 echo'<script type="text/javascript">'
 ,'var lat = json_encode($latitude); 
 var lng = json_encode($longitude); 
 draw(lat,lng);
 '
 ,'</script>';
} 
}
<?php 
$dbh=Database::connect();
Map::createMap(6);
?>

When i excute this code, the following error appears: "$latitude is not defined". var_dump($latitude) is ok. I think the script doesn't recognize $latitude but i don't know why. Any help? thanks

• SomeKittens: Hello! Don't forget to accept an answer, you even get 2 rep for it!

Answer 1

If you're encoding it into JSON, you'll need to wrap it in quotes correctly (you can't call functions inside strings):

echo '<script type="text/javascript">
 var lat = '. json_encode($latitude). '; 
 var lng = '. json_encode($longitude). '; 
 draw(lat,lng);
 </script>';

• Barmar: JSON is (a subset of) Javascript literal syntax, so you don't need to use JSON.parse -- just substitute the result directly into the JS.
• Barmar: It returns the string, but when you echo it into the web page, the quotes are not there.
• Kyle Needham: You could also use $.parseJSON() as a jQuery alternative for better support.
• SomeKittens: @KyleNeedham I don't post jQuery answers to questions that don't have a jQuery tag.

Answer 2

With PHP, single quote are for string literals and will use the name of the variable instead of its value. If you want interpolation (inserting a variable's value into the string), you need to use double quotes.

echo '<script type="text/javascript">',
 "var lat = ". json_encode($latitude) .";
 var lng = ". json_encode($longitude) ."; 
 draw(lat,lng);",
'</script>';

Update: I somehow overlooked the part about json_encode being a PHP call... so the interpolation issue is a moot point, since you just need to concatenate the function's output into the string.

• Cameron Tinker: You need to make sure to concatenate the output from PHP function json_encode to the JavaScript string.

Answer 3

Functions aren't called inside quoted strings. You need to concatenate it:

echo '<script type="text/javascript">
 var lat = ' . json_encode($latitude) . ';
 var lng = ' . json_encode($longitude) . '; 
 draw(lat,lng);
 ';