PHP Grammar - Switch

gistfile1.txt

unticked_statement:
      ...
    | T_SWITCH '(' expr ')' { zend_do_switch_cond(&$3 TSRMLS_CC); } switch_case_list { zend_do_switch_end(&$6 TSRMLS_CC); }
    | ...
;

switch_case_list:
      '{' case_list '}' { $$ = $2; }
    | '{' ';' case_list '}' { $$ = $3; }
    | ':' case_list T_ENDSWITCH ';' { $$ = $2; }
    | ':' ';' case_list T_ENDSWITCH ';' { $$ = $3; }
;

case_list:
    /* empty */ { $$.op_type = IS_UNUSED; }
    | case_list T_CASE expr case_separator { zend_do_extended_info(TSRMLS_C); zend_do_case_before_statement(&$1, &$2, &$3 TSRMLS_CC); } inner_statement_list { zend_do_case_after_statement(&$$, &$2 TSRMLS_CC); $$.op_type = IS_CONST; }
    | case_list T_DEFAULT case_separator { zend_do_extended_info(TSRMLS_C); zend_do_default_before_statement(&$1, &$2 TSRMLS_CC); } inner_statement_list { zend_do_case_after_statement(&$$, &$2 TSRMLS_CC); $$.op_type = IS_CONST; }
;

case_separator:
    ':'
    | ';'
;

why.md

Question

Why does php have the rules on line 9 and 11 (with semicolon in the beginning) in switch_case_list?

---

Examples:

<?php
$foo = 'a';
switch($foo) {
    ;
    case 'a': echo '1'; break;
    case 'b': echo '2'; break;
    default: echo '0'; break;
}
?>

<?php
$foo = 'a';
switch($foo):
    ;
    case 'a': echo '1'; break;
    case 'b': echo '2'; break;
    default: echo '0'; break;
endswitch;
?>