Functions and Arrays of PHP

PHP functions
1. Simple functions
Four elements: return type, function name, argument list, function body

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

Show (); */

2. Functions with return values
/*function Show ()
{
return "Hello";
}

Echo Show (); */

3. Function with parameters

/*function Show ($a)
{
echo $a;
}

Show ("Hello"); */

4. Functions of variable parameters
/*function Sum ()
{
$attr = Func_get_args ();
$n = Func_num_args ();

$sum = 0;
for ($i =0; $i < $n; $i + +)
{
$sum + = $attr [$i];
}
Echo $sum;
}
Sum (1,2,3,4); */

Array
$attr = Array (for each);
$attr 1 = [1,2,3,4,5];
$attr 2[0] = "Hello";
$attr 2[1] = "World";
Var_dump ($attr 2);

1. Indexed arrays
$attr = Array (+/-);
Var_dump ($ATTR);

2. Associative arrays
$attr 1 = Array ("One" =>1, "one" =>2, "3" =>3);
Var_dump ($attr 1);
echo $attr 1[3];

Characteristics:
1. The array can store any type of data
2. Arrays do not create a contiguous area of storage in memory

Iterating through an array
1.for loop traversal, can only traverse indexed array

/*for ($i =0; $i <count ($attr); $i + +)
{
echo $attr [$i]. " <br> ";
}*/

2.foreach traversal, index associations can traverse
/*foreach ($attr as $v)
{
echo $v. " <br> ";
}*/

/*foreach ($attr 1 as $k = $v)
{
echo "{$k}--{$v}<br>";
}
*/

3.each () and list () are combined to iterate through the array//var_dump ($attr 1); Takes the element that the current pointer points to in the array
Var_dump (each ($attr 1));
Var_dump (each ($attr 1));

List ($a, $b, $c, $d) = $attr; Assigns the elements inside the right array to the variables in the argument list


/*while (List ($k, $v) = each ($attr 1))
{
echo "{$k}--{$v}<br>";
}*/

4. Using pointers to iterate through an array
Echo current ($attr 1); Takes the value of the current element pointed to by the pointer
Echo Key ($attr 1); Takes the key of the current element pointed to by the pointer
Next ($attr 1); The pointer is lowered by one
Next ($attr 1);
Prev ($attr 1); Adjust the pointer up one
Echo Key ($attr 1);
End ($attr 1); Move the pointer to the last element
Reset ($attr 1); Reset the pointer

/*for ($i =0; $i <count ($attr 1); $i + +)
{
Echo Key ($attr 1);
Next ($attr 1);
}*/

/*do
{
Echo Key ($attr 1);
}
while (Next ($attr 1)) */
$attr = Array (+/-);
Var_dump ($ATTR);

Functions and Arrays of PHP