What is an array pointer in php

In PHP, the array pointer is the internal organization mechanism of the array. Each array has an internal pointer pointing to its "current" unit (element). This pointer initially points to the current element in the array. A unit; any element in an array can be accessed by moving or changing the position of the pointer. PHP provides multiple built-in functions for controlling array pointers: current(), pos(), key(), next(), prev(), end(), reset().

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

In PHP, the array pointer is internal to the array The organizing mechanism points to an element in an array.

Each array has an internal pointer pointing to its "current" unit (element). This pointer initially points to the first unit in the current array.

You can access any element in the array by moving or changing the position of the pointer. For controlling array pointers, PHP provides the following built-in functions that can be used.

• current(): Returns the current element of the array

• pos(): An alias for current, the usage is the same.

• key(): Read the index value (key value) of the data pointed to by the current pointer.

• next(): Moves the internal pointer in the array to the next cell.

• prev(): Back the internal pointer of the array by one bit.

• end(): Point the internal pointer of the array to the last element.

• reset(): Unconditionally moves the current pointer to the first index position.

current() function

The parameter is an array, passed by reference, and returns the value pointed to by the current array pointer. The pointer moves beyond At the end of the array, return false, return false if the array is empty

The pointer of the array is at the first position of the array by default

<?php
$arr = [11,22,33,44,55,66];
echo current($arr);
?>

key() function

The parameter is an array, passed by reference, and returns the key of the element pointed to by the current pointer. When there is no element in the bit pointed by the pointer, null is returned. An empty array returns null.

<?php $arr = [11,22,33,44,55,66];
var_dump($arr);
echo current($arr)."<br>";   //当前指针指向11 
echo key($arr)."<br>";   //当前元素的键名
?>

next() function

The parameter is an array, passed by reference, moves the array pointer to the next bit, and returns The value of this bit, returns false when there is no element in this bit, and an empty array will also return false

<?php
$arr = [11,22,33,44,55,66];
echo current($arr)."<br>";   //指针指向11
next($arr);                    //指针指向22
echo current($arr)."<br>";   //指针指向22
next($arr);                    //指针指向33
next($arr);                    //指针指向44
echo current($arr)."<br>";   //指针指向44
?>

prev() function

The parameter is an array, pass by reference, move the array pointer to the previous bit, and return the value of that bit. When there is no element in the bit, it returns false. An empty array will also return false

<?php
$arr = [11,22,33,44,55,66];
echo current($arr)."<br>";   //指针指向11
next($arr);                    //指针指向22
next($arr);                    //指针指向33
echo current($arr)."<br>";   //指针指向33
prev($arr);                    //指针指向22
echo current($arr)."<br>";   //指针指向22

?>

end() function

The parameter is an array, passed by reference, moves the internal pointer of an array to the location of the last element of the array, and then returns The value of the last element, returns false if the array is empty

<?php
$arr = [11,22,33,44,55,66];
echo current($arr)."<br>";   //指针指向11
end($arr);                 //指针指向11
echo current($arr)."<br>";   //指针指向66
?>

reset() function

The parameter is a Array, passing by reference, resets the internal pointer of an array to the first position, which is the position of the first element of the array, and then returns the value of the first element, and returns false if the array is empty

<?php
$arr = [11,22,33,44,55,66];
echo current($arr)."<br>";   //指针指向11
next($arr);                    //指针指向22
next($arr);                    //指针指向33
echo current($arr)."<br>";   //指针指向33
reset($arr);               //指针指向11
echo current($arr)."<br>";   //指针指向11
?>

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