For-Each Loop
The foreach construct is a variation of the for loop and is used to
iterate over arrays. There are two different versions of the foreach loop.
The basic foreach loop syntaxes are shown below:
foreach (array as $value) {
statement
}
foreach (array as $key => $value) {
statement
}
The first type of foreach loop is used to loop over
an array denoted by array. During each iteration
through the loop, the current value of the array is assigned to the variable -
$value and the loop counter is incremented by a
value of one. Looping continues until the foreach loop reaches the last element
or upper bound of the given array. During each loop, the value of the variable -
$value can be manipulated but the original
value of the array remains the same.
The following example demonstrates how the foreach
loop is used to iterate over the values of an array:
<?php
$my_array = array('red','green','blue');
$colors = ""; // declare $colors string variable
echo "The different colors include: ";
foreach($my_array as $value) {
$colors .= $value . " ";
}
echo $colors;
?>
During each loop, the color name associated with the current array element is
assigned to a variable - $colors. A single
space " " is also added between each of the color names for display purposes.
When the loop reaches the end of the array, the output below is generated:
The different colors include: red green blue
In order to be able to directly modify array elements within the loop
precede $value with &. In that case the value will be
assigned by reference.
<?php
$my_array = array('red', 'green', 'blue');
foreach ($my_array as &$value) {
if ($value == 'blue') {
$value = 'yellow';
}
}
// $my_array is now array('red', 'green', 'yellow')
unset($value); // break the reference with the last element
?>
The second form of the loop provides the same functionality as the
first, but also assigns the current array element's index or key to
be assigned to the variable - $key on each loop. In the
previous example, the array $my_array contains three elements:
$my_array[0] = "red", $my_array[1] = "green", and
$my_array[2] = "blue". While the variable - $value contains
the array element values: red, green, and blue, the variable $key contains
the array element indices: 0, 1, and 2.
The following example demonstrates how the foreach loop is used to iterate
over the values of an array using the second form:
<?php
$my_array = array('red','green','blue');
$colors = ""; // declare $colors string variable
echo "The different colors include: ";
foreach($my_array as $key => $value) {
$colors .= $my_array[$key] . " ";
}
echo $colors;
?>