The string literal You need to add credenti... `config/services.php`. does not require double quotes, as per coding-style, please use single quotes.
PHP provides two ways to mark string literals. Either with single quotes 'literal' or with
double quotes "literal". The difference between these is that string literals in double quotes
may contain variables with are evaluated at run-time as well as escape sequences.
String literals in single quotes on the other hand are evaluated very literally and the only two
characters that needs escaping in the literal are the single quote itself (\') and the
backslash (\\). Every other character is displayed as is.
Double quoted string literals may contain other variables or more complex escape sequences.
<?php$singleQuoted='Value';$doubleQuoted="\tSingle is $singleQuoted";print$doubleQuoted;
will print an indented: SingleisValue
If your string literal does not contain variables or escape sequences, it should be defined
using single quotes to make that fact clear.
For more information on PHP string literals and available escape sequences see the PHP core