ZEND PHP 5 Certification STUDY GUIDE

58 ” Arrays
If, however, all you need to do is iterate through the entire array from start to finish,
PHP provides a handy shortcut in the form of the foreach() construct:
$array = array(’foo’, ’bar’, ’baz’);
foreach ($array as $key => $value) {
echo "$key: $value";
}
The process that takes place here is rather simple, but has a few important gotchas.
First of all, foreach operates on a copy of the array itself; this means that changes
made to the array inside the loop are not reflected in the iteration—for example,
removing an item from the array after the loop has begun will not cause foreach to
skip over that element. The array pointer is also always reset to the beginning of the
array prior to the beginning to the loop, so that you cannot manipulate it in such a
way to cause foreach to start from a position other than the first element of the array.
PHP 5 also introduces the possibility of modifying the contents of the array directly
by assigning the value of each element to the iterated variable by reference rather
than by value:
$a = array (1, 2, 3);
foreach ($a as $k => &$v) {
$v += 1;
}
var_dump ($a); // $a will contain (2, 3, 4)
While this technique can be useful, it is so fraught with peril as to be something best
left alone. Consider this code, for example:
Licensed to 482634 - Amber Barrow (itsadmin@deakin.edu.au)
$a = array (’zero’,’one’,’two’);
foreach ($a as &$v) {
}
foreach ($a as $v) {
}