Polycops and Robbers (Cops' Thread)
Wow, cracked by Jo King while I'm still typing the explanations lol

'&lt;?php '//'; #@ SPELL,WITH,ME, ,H,E,L,L,O, ,W,O,R,L,D,&quot;'Hello, World!'&quot;
$a = &quot;'Hello, World!'&quot;;
if ([])
 console.log($a);
else {
 for ($i = 1; $i &lt; strlen($a) - 1; $i++)
  echo($a[$i]);
}
// ?&gt;'

Prints 'Hello, World!' (with single quotes) in both JavaScript and PHP. This should be an easy one to solve.
How this works
'&lt;?php '//'; #@ SPELL,WITH,ME, ,H,E,L,L,O, ,W,O,R,L,D,&quot;'Hello, World!'&quot;
JS treats this line as a string '&lt;?php ' followed by a // comment, and PHP prints ' (outside the tag, so literally), then starts the script with open tag, and a string '//', then a # comment.
$a = &quot;'Hello, World!'&quot;;
Both JS and PHP defines the variable a to be the string &quot;'Hello, World!'&quot;.
if ([])
 console.log($a);

In JS, since [] is consider truly, console.log($a) is executed and this prints out the string `&quot;'Hello, World!'&quot;.
else {
 for ($i = 1; $i &lt; strlen($a) - 1; $i++)
  echo($a[$i]);
}

In PHP, since [] is consider falsy, the for loop is executed and this prints out the characters Hello, World! (notice the absence of quotes) subsequently.
// ?&gt;'
In JS this is a comment, but in PHP the close tag ends the script and the ' after the tag is printed out literally.

Yes, the remaining language is Befunge-93.
'&lt;?php '//'; #@ SPELL,WITH,ME, ,H,E,L,L,O, ,W,O,R,L,D,&quot;'Hello, World!'&quot;
&lt; redirects the IP to the end of the line, then &quot;'Hello, World!'&quot; is pushed in reversed order. After that the 15 ,s are used to output the characters (in normal order because of the double reversal). Finally @ terminates the program.