Functions and Arrays

First, the function
Function three elements: 1. Function name 2. parameter List 3. function body
1. Simple functions

function Show () {    echo "Hello";} Show ();

The result of the operation is to display hello on the page

2. Functions with return values

function Show () {   return "Hello";  return value}echo Show ();

The result of the run is the value returned in return value

3. Function with parameters

function Show ($a) {echo $a;} Show ("Hello");

The result of the operation is not a formal parameter, but an argument: Hello

4. Functions of variable parameters

function Sum () {    $attr =func_get_args ();   Gets the parameter Args:func_get_args () passed by the get user;    $n =func_num_args ();    Get quantity Func_num_args ();   Traverse parameter    $Sum =0;   for ($i =0; $i < $n; $i + +)    {       $Sum + = $attr [$i];    }   echo $Sum;} Sum (1);   Values can be changed so that the corresponding values are also changed

The result of the operation is the value in the value

Second, array
Note: 1. Can store any type of data;
2. Not a contiguous area of storage in memory (not contiguous in memory)

$attr =array ();   Defines an empty array $attr1=[1,2];   Defines the array $attr2[0]= "Hello"; Assignment definition array: 0 index Assignment "Hello"

A. Array type:
1. Indexed arrays

$attr = Array (1,2,3,4); Echo $attr [2];   The value that the output index number refers to

2. Associative arrays

$attr 1=array ("One" =>1, "one" =>2, "3" =>3);   K is the one string, value is 1 values,=> conforms to echo $attr 1["one"];  Take value

echo $attr 1[3];  No problem, because the type can be converted automatically, so there is no error

B. Iterating through an array
1.for loops: Only "indexed arrays" can be traversed
COUNT () array length

2.foreach traversal: Both associative arrays and indexed arrays can traverse

Associative arrays:
$attr 1=array ("One" =>1, "one" =>2, "3" =>3); foreach ($attr 1 as $a) {echo $a. <br> ";}

Indexed arrays:
$attr = Array (1,2,3,4), foreach ($attr as $a) {echo $a. <br> ";}

$attr 1=array ("One" =>1, "one" =>2, "3" =>3); foreach ($attr 1 as $k = + $a) {echo $a = "{$k}--{$a}<br>";}

The 3.each () and list () mates iterate through the elements pointed to by the current pointer in the array

$attr 1=array ("One" =>1, "one" =>2, "3" =>3); Var_dump (each ($attr 1));    The first element "one" and 1var_dump (each ($attr 1));   The second element "two" and the 2var_dump (each ($attr 1));   The third element, "3" and 3

$attr = Array (1,2,3,4); list ($a, $b, $c) = $attr;   The assignment is the value in the attr array. The list method is the echo $a to the left of the equals sign;

4. Use the pointer method

The pointer position does not change
Current (); Takes the value of the current element pointed to by the pointer
Key (); Takes the key value of the current element pointed to by the pointer

Variable pointer position
Next (); Executed once, to the downward one

Prev (); Executed once, to raise a

End (); The pointer is transferred directly to the last

Reset (); Pointer reset

Functions and Arrays