Unexpected token | Parse PHP array to JavaScript

Question

When I am parsing a PHP array which is filled with data from a database to JavaScript, I get an error called unexpected token '<' . The code which selectes data from my database is:

$wagennummern = NULL;
$result = $db->query("SELECT * FROM `Wagenbuch`");
while($row = $result->fetch()){
 $wagennummern = $row['Wagennummer'];
}

The code to use this data in JavaScript is:

var wagennummer = <?php echo '["' . implode('", "', $wagennummern) . '"]' ?>;

The Javascript is the line where the error occurs. Can anybody tell me why there is an error and how to fix this?

Answer 1

The particular error message could be caused by a combination of characters that includes a < in the data.

If you want to convert a PHP data structure to a JS data structure, the json_encode, which is compatible with JS. Don't roll your own. Any special character is likely to break your attempt.

var wagennummer = json_encode( $wagennummern );

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It might also be caused by the PHP not being executed at all. This would happen if you weren't loading it from a web server, or if you put it in a file with a .js file extension instead of a .php file.

• Ilijanovic: hmm doesnt you need to parse it too? like JSON.parse(json_encode( $wagennummern )))
• Quentin: @Ifaruki — No. As I said, json_encode is compatible with JS. The generated JSON/JS is not being wrapped in quotes to make it a string literal.

Answer 2

In addition to @Quentin's answer:

I would point out that if your query does not return any row, the variable $wagennummern will be null (first line of your code)

Trying to feed a null value into implode will generate an error, which will be display as HTML, thus creating the unexpected token '<' error.

I would suggest to initialize the $wagennummern variable to an empty array, that way it will not cause any problems if you have no rows. Another solution would be to check for the variable being !== null

• juxwn: What would you suggest to initialize $wagennummer with
• MangledMMU: An empty array, this would allow you to have consistent logic. So it would be $wagennummer = [].