I'm having trouble with a $sql snippets

I'm having trouble with a $sql snippets

in my consultation it cannot run.

In this query the user id of the session instead of showing the id displays the email field eg user@gmail.com

in my sql query in my local test it worked but in the code snippet it doesn't work

$sql = "SELECT id AS aff_id FROM tblclients where email LIKE ".$_SESSION["UserID"];
$aff_id = CustomQuery($sql);
$data = db_fetch_array($aff_id);
echo"". $data["aff_id"];

php Ocorreu o erro…

Erro 626

Consulta de SQL SELECT id AS aff_id FROM tblclients where email LIKE user@gmail.com


the sql query

SELECT id FROM tblclients where email = 'user@gmail.com'