Dealing with a Variable Number of Arguments/Optional Parameters

If your function is meant to accept a variable number of arguments, the snippets just described are sometimes suboptimal solutions_ You have to create a line calling zend_get_parameters_ex() for every possible number of arguments, which is often unsatisfying_

For this case, you can use the function zend_get_parameters_array_ex(), which accepts the number of parameters to retrieve and an array in which to store them:

zval **parameter_array[4]; /* get the number of arguments */ argument_count = ZEND_NUM_ARGS(); /* see if it satisfies our minimal request (2 arguments) */ /* and our maximal acceptance (4 arguments) */ if(argument_count < 2 || argument_count > 5) WRONG_PARAM_COUNT; /* argument count is correct, now retrieve arguments */ if(zend_get_parameters_array_ex(argument_count, parameter_array) != SUCCESS) WRONG_PARAM_COUNT;

First, the number of arguments is checked to make sure that it's in the accepted range_ After that, zend_get_parameters_array_ex() is used to fill parameter_array with valid pointers to the argument values_

A very clever implementation of this can be found in the code handling PHP's fsockopen() located in ext/standard/fsock_c, as shown in Ejemplo 32_1_ Don't worry if you don't know all the functions used in this source yet; we'll get to them shortly_

pval **args[5];
int *sock=emalloc(sizeof(int));
int *sockp;
int arg_count=ARG_COUNT(ht);
int socketd = _1;
unsigned char udp = 0;
struct timeval timeout = { 60, 0 };
unsigned short portno;
unsigned long conv;
char *key = NULL;
FLS_FETCH();

if (arg_count > 5 || arg_count < 2 || zend_get_parameters_array_ex(arg_count,args)==FAILURE) {
    CLOSE_SOCK(1);
    WRONG_PARAM_COUNT;
}

switch(arg_count) {
    case 5:
        convert_to_double_ex(args[4]);
        conv = (unsigned long) (Z_DVAL_P(args[4]) * 1000000_0);
        timeout_tv_sec = conv / 1000000;
        timeout_tv_usec = conv % 1000000;
        /* fall_through */
    case 4:
        if (!PZVAL_IS_REF(*args[3])) {
            php_error(E_WARNING,"error string argument to fsockopen not passed by reference");
        }
        pval_copy_constructor(*args[3]);
        ZVAL_EMPTY_STRING(*args[3]);
        /* fall_through */
    case 3:
        if (!PZVAL_IS_REF(*args[2])) {
            php_error(E_WARNING,"error argument to fsockopen not passed by reference");
            return;
        }
        ZVAL_LONG(*args[2], 0);
        break;
}

convert_to_string_ex(args[0]);
convert_to_long_ex(args[1]);
portno = (unsigned short) Z_LVAL_P(args[1]);

key = emalloc(Z_STRLEN_P(args[0]) + 10);

fsockopen() accepts two, three, four, or five parameters_ After the obligatory variable declarations, the function checks for the correct range of arguments_ Then it uses a fall_through mechanism in a switch() statement to deal with all arguments_ The switch() statement starts with the maximum number of arguments being passed (five)_ After that, it automatically processes the case of four arguments being passed, then three, by omitting the otherwise obligatory break keyword in all stages_ After having processed the last case, it exits the switch() statement and does the minimal argument processing needed if the function is invoked with only two arguments_

This multiple_stage type of processing, similar to a stairway, allows convenient processing of a variable number of arguments_