PHP array

1. What is an array

An array is a collection of data that organizes a series of data to form an operable whole. Each entity of an array contains two items: a key and a value.

2. Declare data

There are two main ways to declare an array in PHP: one is to declare the array using the array() function, and the other is to directly assign values ​​to the array elements.

<1>array() function declares array array([mixed...]) The syntax of parameter mixed is key=>value

For example,

$array=array(" 1"=>"Editor","2"=>"Cheng","3"=>"Word","4"=>"Dictionary");

print_r($array);

echo "
";

echo $array[1]; // Note: The subscript starts from 0 by default

echo $array[2];

echo $array[3];

echo $ array[4];

?>

<2> Directly assign values ​​to array elements. This method of array creation is better if you don't know the size of the array when you create it, or if the size of the array may change when you actually write the program.

For example,

$array[1]="I";

$array[2]="love";

$array[3]="PHP";

print_r($array ); // Output the structure of the created array

?>

3. Type of array

PHP supports two types of arrays: indexed array and associative array, the former uses numbers As keys, the latter uses strings as keys.

4. Output Array

In PHP, the output of array elements can be achieved through echo and print statements, but this can only output a certain element in the array; to output the array structure, use print_r () function, its syntax: print_r (mixed expression), if the parameter expression is an ordinary integer, character or real variable, the variable itself will be output. If the parameter is an array, the variable will be displayed in the order of a certain key value and element. all elements in the array.

5. Array construction

One-dimensional array:

When the elements of an array are variables, it is called a one-dimensional array.

Declare a one-bit array: type specifier array name [constant expression];

two-dimensional array:

When the element of an array is a one-bit array, it is called a two-dimensional array.

For example,

$str = array (

" Network Programming Language "=>array ("PHP", "JSP", "ASP"),

" Sports "=>array ("m"=>" Football ","n"=>" Basketball "));

print_r ( $str) ;

?>

6. Traverse the array

Traverse the array All elements are a common operation, and queries or other functions can be completed during the traversal process. There are many ways to traverse arrays in PHP. The two most commonly used methods are introduced below.

<1> Use the foreach structure to traverse the array;

<2> Use the list() function to traverse the array. The list() function can only be used for numerically indexed arrays, and the numerical index starts from 0.

Example: Combined use of list() and each() to authenticate user login:

// Output user login information

while(list($name,$value)=each($_POST)) {

if($name!="submit"){

echo "$name=$value
";

}

}

?>

7. Count the number of array elements

In PHP, use the count() function to count the number of elements in an array. The syntax is: int coun(mixed array[,int mode]), where the parameter array is a required parameter and mode is an optional parameter. If COUNT is selected —— RECURSIVE( or 1), this function will recursively search the array of arrays. For example,

$array = array("php" => array("PHP Function Reference Collection", "PHP Program Development Example Collection", "PHP Database System Development Complete Manual"),

"asp" => array("ASP Experience and Skills Collection ")

); // Declare a two-dimensional array

echo count($array,COUNT_RECURSIVE); // Recursively count the number of array elements, and the running result is 6

?> array(5,26,37,18,9,42,88,66);

$array1=sort($array);

for($i=0;$i

echo $array[$i]."  ";

}

echo "
";

$array1=rsort($array);

for($i=0;$i

echo $array[$i " ksort( ) and asort() to sort associative arrays

If you use associative arrays, you need to keep the order of keys and values ​​consistent after sorting. This requires using ksort() and asort() functions

, such as,

$array=array('php'=>1,'jsp'=>2,'asp'=>3);

ksort($array);

print_r($array);

echo "
";

asort($array);

print_r($array);

?>

Run result:

Array ( [asp] => 3 [jsp] => 2 [php] => 1 )

Array ( [php] => 1 [jsp] => 2 [asp] => 3 )