c - Can I pass the string in PHP extension by reference with separating from other variables? -

i have example code:

zend_begin_arg_info(arginfo_refstring, 0)     zend_arg_info(1, s1) zend_end_arg_info()  const zend_function_entry refstring_functions[] = {     php_fe(refstring, arginfo_refstring)     php_fe_end };  php_function(refstring) {     char *s1;     int s1_len;      if (zend_parse_parameters(zend_num_args() tsrmls_cc, "s", &s1, &s1_len) == failure) {         return;     }      s1[0] = 'x'; } 

and php code:

$s1 = 'hello'; $s2 = $s1; refstring($s1); var_dump($s1, $s2); 

i expect:

string(5) "xello" string(5) "hello" 

but got:

string(5) "xello" string(5) "xello" 

how can separate $s2 $s1, keep ability change $s1 inside function?

i known separate_zval , co., did not help...

this happens because of mechanism called copy on write.

after lines:

$s1 = 'hello'; $s2 = $s1; 

$s1 , $s2 both independent variables (zvals), point same(!) data in memory - because both share same value, meaning none of them has been changed far.

if would:

$s1 = 'foo'; 

... php internally update zval behind $s1 in way it's value points different portion of memory.

however, since modifying value in extension function, function need take care on itself:

php_function(refstring) {     zval *s1;     char *string;      if (zend_parse_parameters(zend_num_args() tsrmls_cc, "z", &s1)         != success     ) {         return;     }         // copy value before writing     string = strdup(s1->value.str.val);     string[0] = 'x';      zval_string(s1, string, 1); } 

note i'm using zval * rather using pure string input parameter.

further note that, above function works expected. however, i'm not sure if there macro purpose can used more elegantly.