Function declaration (in php_xdebug.h):
PHP_FUNCTION(xdebug_start_error_collection);

Function definition (in xdebug.c):
PHP_FUNCTION(xdebug_start_error_collection)
{
    if (XG(do_collect_errors) == 1) {
        php_error(E_NOTICE, "Error collection was already started");
    }
    XG(do_collect_errors) = 1;
}

Function entry array (in xdebug.c):
zend_function_entry xdebug_functions[] = {
...
    PHP_FE(xdebug_start_error_collection,     NULL)
...
    {NULL, NULL, NULL}
};