Summary of the key and value methods of obtaining arrays in PHP, summary of obtaining arrays in PHP_PHP tutorial

Summary of PHP's method of obtaining the keys and values ​​of an array, summary of PHP's method of obtaining the array

The example in this article describes the method of obtaining the keys and values ​​of an array in PHP. Share it with everyone for your reference. The details are as follows:

When using an array, you often need to traverse the array. It is often necessary to iterate through an array and get the individual keys or values ​​(or get both keys and values), so not surprisingly, PHP provides some functions for this purpose. Many functions perform two tasks, not only obtain the key or value at the current pointer position, but also move the pointer to the next appropriate position.

Get the current array key key()

The key() function returns the key at the current pointer position in input_array. Its form is as follows:

mixed key(array array)

The following example outputs the keys of the $fruits array by iterating through the array and moving the pointer:

$fruits = array("apple"=>"red", "banana"=>"yellow");
while ($key = key($fruits)) {
   printf("%s <br />", $key);
   next($fruits);
}
// apple 
// banana

Note that the pointer will not be moved each time key() is called. For this purpose, the next() function needs to be used. The only function of this function is to complete the task of advancing the pointer.

Get the current array value current()

The current() function returns the array value at the current pointer position in the array. Its form is as follows:

mixed current(array array)

Let’s modify the previous example. This time we want to get the array value:

$fruits = array("apple"=>"red", "banana"=>"yellow");
while ($fruit = current($fruits)) {
   printf("%s <br />", $fruit);
   next($fruits);
}
// red 
// yellow 

Get the current array key and value each()

The each() function returns the current key/value pair of input_array and advances the pointer one position. Its form is as follows:

array each(array array)

The returned array contains four keys, key 0 and key contain the key name, and key 1 and value contain the corresponding data. If the pointer is at the end of the array before each() is executed, false is returned.

$fruits = array("apple", "banana", "orange", "pear");
print_r ( each($fruits) );
// Array ( [1] => apple [value] => apple [0] => 0 [key] => 0 )

each() is often used in conjunction with list() to iterate over an array. This example is similar to the previous example, but the entire array is output in a loop:

$fruits = array("apple", "banana", "orange", "pear");
reset($fruits);
while (list($key, $val) = each($fruits))
{
   echo "$key => $val<br />";
}
// 0 => apple
// 1 => banana
// 2 => orange
// 3 => pear

Because assigning one array to another array will reset the original array pointer, in the above example if we assign $fruits to another variable inside the loop, it will cause an infinite loop.

This completes array traversal.

I hope this article will be helpful to everyone’s jQuery programming.