PHP将数组追加到数组引用

Question

I have a function which return reference to an array (globals are used for simplicity, actually these arrays are elements of some big tree structure):

$array1;
$array2;

function &foo($arg){
  //deduce from $arg reference to which array should be returned
  if(...) {
    global $array1;
    return $array1;
  } else {
    global $array2;
    return $array2;
  }
}

Then I need to append another array to the one returned with this function (so that initial array was changed):

$arrayToAppend = array('a','b');
$arrayToChange = &foo($arg);
$arrayToChange = array_merge($arrayToChange, $arrayToAppend);

Is it correct syntax for what I want to do? Does it change referenced array? Are there any pitfalls I should know? (pitfalls about reference stuff, not about merging assosiative arrays etc.)

Answer 1

You are mixing things up. You should only use & in front of a parameter in your function (if the parameter is a simple type, so no object) and you want the content of that parameter to change.

Example:

<?php

$arrayToChange = array('a', 'b');
$arrayToAppend = array('c', 'd');
mergeArrays($arrayToChange, $arrayToAppend); 

// $arrayToChange will now contain 'a', 'b', 'c', 'd' 

function mergeArrays(& $array, $arrayToAppend)
{
  $array = array_merge($array, $arrayToAppend);
} 

//Note: This is not the way you should do it. 
//A function best returns a result. 
//This just illustrates how you can change the content of a parameter