Syntax Error when passing non-existing variable from PHP into JavaScript

Question

I have the following code that passes a variable (EmployeeID) from PHP into JavaScript:

EmployeeID= <?php echo "$EmployeeID"?>;

The issue is that the variable EmployeeID in PHP might not exist, in which case, after I run the JavaScript code, I receive an error

Uncaught SyntaxError: Unexpected token

When I look into the Source Code in Dev Tools I can see this:

EmployeeID = ;

What would be the best way to handle this error? I tried

if (EmployeeID == null){
    EmployeeID = "0"; //0 - stands for generic variable in case if EmployeeID doesn't exist
}

Any help would be greatly appreciated!

u_mulder · Accepted Answer · 2018-10-05 19:19:50Z

2

This php code outputs either $EmployeeID value or 0, so your js var holds 0 when $EmployeeID has falsy value:

var EmployeeID = <?php echo $EmployeeID ? $EmployeeID : 0 ?>;

answered Oct 5, 2018 at 19:19

u_mulder

54.8k5 gold badges54 silver badges72 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Luke Over a year ago

Works great! Thanks!

Vitalijs G. Over a year ago

May be it is better to check isset($EmloyeeID) if variable might not exist

u_mulder Over a year ago

@VitalijsG. indeed it maybe. But I just showed an example how to always output something. Even ?? operator can be used, which eliminates the need for isset.

miken32 Over a year ago

Yeah I would have gone with null coalesce. DRY and all that, and will avoid undefined variable notices in the log file in case it's not set.

Francisco Hahn · Accepted Answer · 2018-10-08 12:52:48Z

1

As the first answer states, a shothanded if is a great solution for this case

<?php echo $EmployeeID ? $EmployeeID : 0 ?>

But in this case the output will be 0 if $EmployeeID == 0, null, false, '', for this case i strongly recomment you to use the method ´isset()´, as the variable may not be declared (for example if an employeeID is actually 0)

<?php 
  if(isset($EmployeeID)){
       // Do something here
  } else {
       // whatever u need
  }

For a better refference about php-isset

edited Oct 8, 2018 at 12:52

answered Oct 5, 2018 at 19:32

Francisco Hahn

4355 silver badges10 bronze badges

Comments

miken32 · Accepted Answer · 2018-10-05 20:48:11Z

0

So the other answers will likely work fine for what I'm assuming is a numeric value, but in case you have a text value, you'll want to ensure it's properly escaped for JavaScript. json_encode() is perfect for this. I'd do something like this:

EmployeeID= <?= json_encode($EmployeeID ?? null) ?>;

This will ensure that any text is properly escaped, and the null coalesce operator gives you a default without triggering notices about undefined variables in case the variable doesn't have a value.

answered Oct 5, 2018 at 20:48

miken32

42.5k16 gold badges127 silver badges177 bronze badges

Collectives™ on Stack Overflow

Syntax Error when passing non-existing variable from PHP into JavaScript

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related