PHP prev() Function
Definition
The prev() function moves the internal pointer to the previous element in the array and output its value.
Syntax
PHP prev() Function has the following syntax.
prev(array)Parameter
| Parameter | Is Required | Description |
|---|---|---|
| array | Required. | Array to use |
Related methods
| Method | Description |
|---|---|
| next() | moves the pointer to, and outputs the next element in the array |
| current() | returns the value of the current element in an array |
| end() | moves the pointer to, and outputs the last element in the array |
| reset() | moves the pointer to the first element of the array |
| each() | returns the current element key and value, and moves the pointer forward |
Example 1
The next() and prev() functions
move the cursor pointer forward or backward one element respectively, returning
the value of the element now pointed to.
If cannot return a value, it will return false.
<?PHP/*www . j ava 2 s .c o m*/
$array = array("A", "B", "C", "D", "E");
print end($array);
while($val = prev($array)) {
print $val;
}
?>
The code above generates the following result.
Example 2
Using prev() and next() is more difficult when using arrays that have holes.
For example:
<?PHP//from w w w . j a va2 s . com
$array["a"] = "Foo";
$array["b"] = "";
$array["c"] = "Baz";
$array["d"] = "Wom";
print end($array);
while($val = prev($array)) {
print $val;
}
?>
The empty value at key b causes both prev() and
next() to return false, prematurely ending the loop.
The code above generates the following result.
Example 3
Output the value of the current, next and previous element in the array:
<?php//from www .j a v a2s . co m
$people = array("Peter", "Joe", "Glenn", "Cleveland");
echo current($people) . "\n";
echo next($people) . "\n";
echo prev($people);
?>
The code above generates the following result.
Example 4
A demonstration of all related methods:
<?php//from w w w . j av a 2 s. c o m
$people = array("A", "B", "C", "D");
echo current($people) . "\n"; // The current element is A
echo next($people) . "\n"; // The next element of A is B
echo current($people) . "\n"; // Now the current element is B
echo prev($people) . "\n"; // The previous element of B is A
echo end($people) . "\n"; // The last element is D
echo prev($people) . "\n"; // The previous element of D is C
echo current($people) . "\n"; // Now the current element is C
echo reset($people) . "\n"; // Moves the internal pointer to the first element of the array, which is A
echo next($people) . "\n"; // The next element of A is B
print_r (each($people)); // Returns the key and value of the current element (now B), and moves the internal pointer forward
?>
The code above generates the following result.
