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

Hello! Don't forget to accept an answer, you even get 2 rep for it! — SomeKittens
– SomeKittens, Commented Apr 4, 2014 at 21:13

SomeKittens · Accepted Answer · 2014-04-04 19:52:17Z

6

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>';

edited Apr 4, 2014 at 19:52

answered Apr 4, 2014 at 19:46

SomeKittens

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4 Comments

Barmar Over a year ago

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 Over a year ago

It returns the string, but when you echo it into the web page, the quotes are not there.

Kyle Needham Over a year ago

You could also use $.parseJSON() as a jQuery alternative for better support.

SomeKittens Over a year ago

@KyleNeedham I don't post jQuery answers to questions that don't have a jQuery tag.

Cameron Tinker · Accepted Answer · 2014-04-04 20:04:05Z

4

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.

edited Apr 4, 2014 at 20:04

Cameron Tinker

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answered Apr 4, 2014 at 19:46

Greg

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1 Comment

Cameron Tinker Over a year ago

You need to make sure to concatenate the output from PHP function json_encode to the JavaScript string.

Barmar · Accepted Answer · 2014-04-04 19:52:16Z

1

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);
     ';

answered Apr 4, 2014 at 19:52

Barmar

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