Entry

How do I implement a stack?

How do I emulate PERL's push() and pop()?

May 26th, 2000 02:09
Bruce Morrison, Leon Atkinson,

The following functions implement a stack (First In, Last Out)
in PHP3.  If using PHP4, use the built-in functions
(array_push, array_pop).
Warning: This implementation of a stack does not work if you push after
popping. Try
        print(push('Apple', $myArray) . " items on stack<BR>\n");
	print(push('Ball', $myArray) . " items on stack<BR>\n");
	print(push('Cat', $myArray) . " items on stack<BR>\n");
	print(pop($myArray) . "<BR>\n");	
	print(pop($myArray) . "<BR>\n");	
	print(pop($myArray) . "<BR>\n");
        print(push('Apple', $myArray) . " items on stack<BR>\n");
	print(push('Ball', $myArray) . " items on stack<BR>\n");
	print(push('Cat', $myArray) . " items on stack<BR>\n");
	print(pop($myArray) . "<BR>\n");	
	print(pop($myArray) . "<BR>\n");	
	print(pop($myArray) . "<BR>\n");
after defining the functions.
to fix 
//removes item from stack
function pop(&$array)
{
  //get size of stack
  $count = count($array);
  //get the item
  $item = $array[$count - 1];
  //delete it from the stack
  for ($i = 0; $i <= $count-2; $i++) {
    $tmp_array[]=$array[$i];
  }
  $array=$tmp_array;
  //return the item
  return($item);
}
<?
	//adds an item to the stack
	function push($item, &$array)
	{
		//add item to end of array
		$array[] = $item;
		//return the size of the stack
		return(count($array));
	}
	//removes item from stack
	function pop(&$array)
	{
		//get size of stack
		$count = count($array);
		//get the item
		$item = $array[$count - 1];
		//delete it from the stack
		unset($array[$count - 1]);
		//return the item
		return($item);
	}
	print(push('Apple', $myArray) . " items on stack<BR>\n");
	print(push('Ball', $myArray) . " items on stack<BR>\n");
	print(push('Cat', $myArray) . " items on stack<BR>\n");
	print(pop($myArray) . "<BR>\n");	
	print(pop($myArray) . "<BR>\n");	
	print(pop($myArray) . "<BR>\n");
?>