PHP Code related issues

PHP Code issues
$filename = ' Strval ($id). ". gif";
Want to add a path to the picture on the right such as this $filename =images/' Strval ($id). GIF "';
Determine the ' Strval ($id) under the Images folder. GIF "' picture is present.
But the code does not read, where the code is wrong
I am a novice php request advice Thank you!
------Solution--------------------
There should be no quotes, but you have
You don't have the quotes.

$filename = "images/". Strval ($id). ". gif";
------Solution--------------------
Single quotation marks contain strings that are exported as strings
Double quotes contain strings that parse the special characters inside, such as $id
And the efficiency of single quotes is faster than double quotes
------Solution--------------------
You can write it like this.

