Porting a php5 module to php 7 and zend_string issues when compiling

Question

I'm porting a php5 tot php7, but don't understand how to correctly use zend_string since it gives me errors when compiling. I followed the phpng guide on the changes in php7. Most functions i could port easily, but this function is giving me a headache.

The php5 version of the module looks like this:

PHP_FUNCTION(swe_houses)
{
char *arg = NULL;
int hsys_len, rc;
char *hsys = NULL;
double tjd_ut, geolat, geolon;
double cusps[37], ascmc[10]; 
int i, houses;
zval *cusps_arr, *ascmc_arr;

if(ZEND_NUM_ARGS() != 4) WRONG_PARAM_COUNT;

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ddds",
        &tjd_ut, &geolat, &geolon, &hsys, &hsys_len) == FAILURE) {
    return;
}
if (hsys_len < 1)
    return;

rc = swe_houses(tjd_ut, geolat, geolon, hsys[0], cusps, ascmc);

/* create 2 index array, and 1 assoc array */
array_init(return_value);

MAKE_STD_ZVAL(cusps_arr);
array_init(cusps_arr);

if (hsys[0] == 'G')
    houses = 37;
else
    houses = 13;

for(i = 0; i < houses; i++)
    add_index_double(cusps_arr, i, cusps[i]);

MAKE_STD_ZVAL(ascmc_arr);
array_init(ascmc_arr);
for(i = 0; i < 10; i++)
    add_index_double(ascmc_arr, i, ascmc[i]);

add_assoc_zval(return_value, "cusps", cusps_arr);
add_assoc_zval(return_value, "ascmc", ascmc_arr);
add_assoc_long(return_value, "rc", rc);
}

So the guide says i need to replace "char *hsys" into "zend_string *hsys = null". And replaced "MAKE_STD_ZVAL" functions to "ZVAL_NEW_ARR". In the zend_parse_parameters function i changed the "s" parameter to "S".

So eventually i changed the code to look like this:

PHP_FUNCTION(swe_houses)
{
zend_string *arg = NULL;
size_t hsys_len, rc;
zend_string *hsys = NULL;
double tjd_ut, geolat, geolon;
double cusps[37], ascmc[10]; 
size_t i, houses;
zval *cusps_arr, *ascmc_arr;

if(ZEND_NUM_ARGS() != 4) WRONG_PARAM_COUNT;

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "dddS",
        &tjd_ut, &geolat, &geolon, &hsys, &hsys_len) == FAILURE) {
    return;
}
if (hsys_len < 1)
    return;

rc = swe_houses(tjd_ut, geolat, geolon, hsys[0], cusps, ascmc);

/* create 2 index array, and 1 assoc array */
array_init(return_value);

/*******************************/
/*      removed for php 7      */
/*   MAKE_STD_ZVAL(cusps_arr); */
/*******************************/

ZVAL_NEW_ARR(cusps_arr);
array_init(cusps_arr);

if (hsys[0] == 'G')
    houses = 37;
else
    houses = 13;

for(i = 0; i < houses; i++)
    add_index_double(cusps_arr, i, cusps[i]);

/*******************************/
/*      removed for php 7      */   
/*    MAKE_STD_ZVAL(ascmc_arr); */
/*******************************/

ZVAL_NEW_ARR(ascmc_arr);
array_init(ascmc_arr);


for(i = 0; i < 10; i++)
    add_index_double(ascmc_arr, i, ascmc[i]);

add_assoc_zval(return_value, "cusps", cusps_arr);
add_assoc_zval(return_value, "ascmc", ascmc_arr);
add_assoc_long(return_value, "rc", rc);
}

But on compilling it gives me the following errors:

/home/hermes/php-sweph/latest/php-sweph/sweph.c:926:42: error:   
incompatible type for argument 4 of ‘swe_houses’
rc = swe_houses(tjd_ut, geolat, geolon, hsys[0], cusps, ascmc);
                                      ^
In file included from /home/hermes/php-sweph/latest/php- 
sweph/sweph.c:23:0:

/usr/local/include/swephexp.h:742:16: note: expected ‘int’ but argument is       

of type ‘zend_string {aka struct _zend_string}’
ext_def( int ) swe_houses(
            ^
/home/hermes/php-sweph/latest/php-sweph/sweph.c:939:14: error: invalid    
operands to binary == (have ‘zend_string {aka struct _zend_string}’ and        
‘int’)
if (hsys[0] == 'G')

Answer 1

First things first, zend_string is not at all like a char* or char[], therefore you cannot access elements simply by referencing an index. It's a struct not an array.

This is what zend_string is:

struct _zend_string {
    zend_refcounted_h gc;
    zend_ulong        h;                /* hash value */
    size_t            len;
    char              val[1];
};

What I would do is change hsys back to char* so you can use the regular string functions and reference the elements like an array.

Here is an example of what I think will work and I will comment what I changed about it.

PHP_FUNCTION(swe_houses) {
    char *arg = NULL;                 /* char */
    size_t hsys_len, rc;
    char *hsys = NULL;                /* char */
    double tjd_ut, geolat, geolon;
    double cusps[37], ascmc[10]; 
    size_t i, houses;
    zval cusps_arr, ascmc_arr;        /* removed pointer */

    if(ZEND_NUM_ARGS() != 4) WRONG_PARAM_COUNT;

    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ddds",
        &tjd_ut, &geolat, &geolon, &hsys, &hsys_len) == FAILURE) {
        return;
    }
    if (hsys_len < 1)
        return;

    rc = swe_houses(tjd_ut, geolat, geolon, hsys[0], cusps, ascmc);

    /* create 2 index array, and 1 assoc array */
    array_init(return_value);

    /* ZVAL_NEW_ARR(cusps_arr); unneeded */
    array_init(&cusps_arr); /* added & */

    if (hsys[0] == 'G')
        houses = 37;
    else
        houses = 13;

    for(i = 0; i < houses; i++)
        add_index_double(&cusps_arr, i, cusps[i]); /* added & */

    /* ZVAL_NEW_ARR(ascmc_arr); unneeded */
    array_init(&ascmc_arr); /* added & */


    for(i = 0; i < 10; i++)
        add_index_double(&ascmc_arr, i, ascmc[i]); /* added & */

    /* this may cause issues, not sure though */
    add_assoc_zval(return_value, "cusps", &cusps_arr); /* added & */
    add_assoc_zval(return_value, "ascmc", &ascmc_arr); /* added & */
    add_assoc_long(return_value, "rc", rc);
}