Description:
------------
In regular expressions an unescaped minus character (-) in character classes is usually used to declare a range. However when the range makes no sense, it is treated as a literal minus character. This seems still to be true for most occasions in 7.3-dev except for one special combination, where the minus sits between a shortcut character class and a dollar sign. Eg. /[\w-$]/. Previous PHP versions would treat this as word characters, minus and dollar. PHP 7.3-dev throws an error.

Test script:
---------------
<?php                                                                           
                                                                                
$tests = [                                                                      
    '/[\w-$]/',                                                                 
    '/[\w-]/',                                                                  
    '/[-\w]/',                                                                  
    '/[$-]/',                                                                   
    '/[-$]/',                                                                   
];                                                                              
                                                                                
echo PHP_VERSION;                                                               
echo "\n";                                                                      
                                                                                
foreach($tests as $test) {                                                      
    echo "$test\n";                                                             
    preg_match($test,'');                                                       
}

Expected result:
----------------
7.2.3
/[\w-$]/
/[\w-]/
/[-\w]/
/[$-]/
/[-$]/

Actual result:
--------------
7.3.0-dev
/[\w-$]/

Warning: preg_match(): Compilation failed: invalid range in character class at offset 3 in /var/www/test.php on line 16
/[\w-]/
/[-\w]/
/[$-]/
/[-$]/