What are the array pointer operation functions in php?

In PHP, an array is an important data structure that allows us to store a set of data in a variable. Using an array, we can access and manipulate its elements by index. PHP provides many useful functions to manipulate arrays, including array pointer manipulation functions.

Array pointer operation functions refer to those functions that can be used to operate array pointers. An array pointer is an internal pointer that points to the current array element. When traversing an array, we can use pointers to access and manipulate elements in the array.

The following are commonly used PHP array pointer operation functions:

1. current(): This function returns the value of the current array element pointed to by the pointer. If the pointer points to no element, returns false.
2. key(): This function returns the key of the current array element pointed to by the pointer. If the pointer points to no element, null is returned.
3. next(): This function moves the pointer forward one position and returns the value of the array element pointed to by the moved pointer. If the pointer has reached the last element, returns false.
4. prev(): This function moves the pointer backward one position and returns the value of the array element pointed to by the moved pointer. If the pointer has reached the first element, returns false.
5. end(): This function moves the pointer to the last element of the array and returns the value of the element. If the array is empty, returns false.
6. reset(): This function moves the pointer to the first element of the array and returns the value of the element. If the array is empty, returns false.
7. each(): This function returns the key and value of the array element pointed to by the current pointer, returned in array form. Then move the pointer forward one position. If the pointer has reached the last element, returns false.

For example, we can use these functions to iterate over an array in the following way:

$fruits = array("apple", " banana", "orange");

echo current($fruits) . "
"; // apple
echo key($fruits) . "
"; // 0

next($fruits);
echo current($fruits) . "
"; // banana
echo key($fruits) . "
"; // 1

next($fruits);
echo current($fruits) . "
"; // orange
echo key($fruits) . "
"; // 2

prev($fruits);
echo current($fruits) . "
"; // banana
echo key($fruits) . "
"; // 1

reset($fruits);
echo current($fruits) . "
"; // apple
echo key($fruits) . "
"; // 0

end($fruits);
echo current($fruits) . "
"; // orange
echo key($fruits) . "
"; // 2

while ($fruit = each($fruits)) {

echo $fruit["key"] . " => " . $fruit["value"] . "
";

}
?>
In the above example, we use current( ) function to get the value of each element, and the key() function to get the key of each element. We also use next() and prev() functions to move the array pointer forward and backward. Additionally, we use the reset() and end() functions to move the pointer to the beginning and end of the array. Finally, we use the each() function to iterate through the entire array and get the key and value of each element. 
In addition to the functions listed above, there are other useful array pointer operation functions, such as: current(), key(), next(), prev(), end(), reset( ), each(), pos(), prev(), next(), array_slice() and array_splice(), etc. These functions can help us operate and traverse PHP arrays more conveniently, making our development work more efficient and convenient. 
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