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copied!<p>Your code works fine, there is no bug, and it is independent to PHP 4 or 5. Maybe it helps if this is simply explained to you.</p> <p>Let's go through the example which does not work in your eyes, just looking what actually happens:</p> <pre><code>// step 1 $foo = array(); # 1. $foostack = array( &$foo ); # 2. </code></pre> <ul> <li>1.: You initialize the variable <code>$foo</code> to an empty array.</li> <li>2.: You initialize the variable <code>$foostack</code> to an array and the first element of the array is an alias of the variable <code>$foo</code>. This is exactly the same as writing: <code>$foostack[] =& $foo;</code></li> </ul> <p>On to the next step:</p> <pre><code>// step 2 $last = array_pop($foostack); # 3. array_push($last, 'hello'); # 4. array_push($foostack, &$last); # 5. </code></pre> <ul> <li>3.: You assign the last element's <em>value</em> of the array <code>$foostack</code> to <code>$last</code> and you remove the last element from the array <code>$foostack</code>. <strong><em>Note:</em></strong> <code>array_pop</code> returns a value, not a reference.</li> <li>4.: You add <code>'hello'</code> as a new element to an empty array in <code>$last</code>.</li> <li>5.: You add <code>&$last</code> as a new element to <code>$foostack</code>;</li> </ul> <p>So which variables do we have now?</p> <ul> <li>First of all <code>$foo</code> which just contains an empty array. The last element of <code>$foostack</code> was once reference to it (2.), but you have removed that directly after (3.). As <code>$foo</code> and it's value has not been changed any longer, it's just an empty array <code>array()</code>.</li> <li>Then there is <code>$last</code>, which got an empty array in 3.. That's just an empty array, it's a value not a reference. In (4.) you add the string <code>'hello'</code> as first element to it. <code>$last</code> is an array with one string element in there.</li> <li>Then there is <code>$foostack</code>. It's an array that get's a reference to <code>$foo</code> in (2.), then that reference is removed in (3.). Finally an alias to <code>$last</code> is added to it.</li> </ul> <p>This is exactly what the rest of your code outputs:</p> <pre><code>echo count($foostack[0]) .';'. count($foo); </code></pre> <p><code>$foostack[0]</code> is the alias to <code>$last</code> - the array with the string <code>'hello'</code> as only element, while <code>$foo</code> is just <code>$foo</code>, the empty array <code>array()</code>.</p> <p>It makes no difference if you execute that with PHP 4 or 5.</p> <hr> <p>As you write that's "wrong", I assume you were just not able to achieve what you wanted. You're probably looking for a function that is able to return the reference to the last element of an array before removing it. Let's call that function <code>array_pop_ref()</code>:</p> <pre><code>// step 1 $foo = array(); $foostack = array( &$foo ); // step 2 $last =& array_pop_ref($foostack); array_push($last, 'hello'); array_push($foostack, &$last); // results echo count($foostack[0]) .';' .count($foo); # 1;1 </code></pre> <p>The <code>array_pop_ref</code> function:</p> <pre><code>function &array_pop_ref(&$array) { $result = NULL; if (!is_array($array)) return $result; $keys = array_keys($array); $end = end($keys); if (false === $end) return $result; $result =& $array[$end]; array_pop($array); return $result; } </code></pre>

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