Question

I’m writing a PHP extension that takes a reference to a value and alters it. Example PHP:

$someVal = 'input value'; TestPassRef($someVal); // value now changed 

What’s the right approach?

Answer 1

Edit 2011-09-13: The correct way to do this is to use the ZEND_BEGIN_ARG_INFO() family of macros – see Extending and Embedding PHP chapter 6 (Sara Golemon, Developer’s Library).

This example function takes one string argument by value (due to the ZEND_ARG_PASS_INFO(0) call) and all others after that by reference (due to the second argument to ZEND_BEGIN_ARG_INFO being 1).

const int pass_rest_by_reference = 1; const int pass_arg_by_reference = 0;  ZEND_BEGIN_ARG_INFO(AllButFirstArgByReference, pass_rest_by_reference)    ZEND_ARG_PASS_INFO(pass_arg_by_reference) ZEND_END_ARG_INFO()  zend_function_entry my_functions[] = {     PHP_FE(TestPassRef, AllButFirstArgByReference) };  PHP_FUNCTION(TestPassRef) {     char *someString = NULL;     int lengthString = 0;     zval *pZVal = NULL;      if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, 'sz', &someString, &lengthString, &pZVal) == FAILURE)     {         return;     }      convert_to_null(pZVal);  // Destroys the value that was passed in      ZVAL_STRING(pZVal, 'some string that will replace the input', 1); } 

Before adding the convert_to_null it would leak memory on every call (I’ve not whether this is necessary after adding ZENG_ARG_INFO() calls).