php數組總結篇(一）

數組
1.數組的下標是整型數值或者是字串類型。
eg1．索引數組的鍵是______，關聯陣列的鍵是______。
2.字串作為索引的時候，應加上引號。常量或者變數不用加引號，否則無法編譯。
在php中，沒有引號的字串會自動產生一個裸字串，而 PHP 可能會在以後定義此常量，不幸的是你的代碼中有同樣的名字，那麼這個字串就被重新賦值。
eg2.<?php
// 顯示所有錯誤
error_reporting(E_ALL);
$arr = array('fruit' => 'apple', 'veggie' => 'carrot');
// 正確
print $arr['fruit']; // apple
print $arr['veggie']; // carrot
// 不正確。This works but also throws a PHP error of
// level E_NOTICE because of an undefined constant named fruit
//
// Notice: Use of undefined constant fruit - assumed 'fruit' in...
print $arr[fruit]; // apple
// Let's define a constant to demonstrate what's going on. We
// will assign value 'veggie' to a constant named fruit.
define('fruit','veggie');
// Notice the difference now
print $arr['fruit']; // apple
print $arr[fruit]; // carrot
// The following is okay as it's inside a string. Constants are not
// looked for within strings so no E_NOTICE error here
print "Hello $arr[fruit]"; // Hello apple
// With one exception, braces surrounding arrays within strings
// allows constants to be looked for
print "Hello {$arr[fruit]}"; // Hello carrot
print "Hello {$arr['fruit']}"; // Hello apple
// This will not work, results in a parse error such as:
// Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
// This of course applies to using autoglobals in strings as well
print "Hello $arr['fruit']";
print "Hello $_GET['foo']";
// Concatenation is another option
print "Hello " . $arr['fruit']; // Hello apple
?>
3.索引值問題
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name'] = 'apple';
$a[] = 4; // key will be 0
$b[] = 'a'; // key will be 0
$b[] = 'b'; // key will be 1
$b[] = 'c'; // key will be 2
switching = array( 10, // key = 0
5 => 6,
3 => 7,
'a' => 4,
11, // key = 6 (maximum of integer-indices was 5)
'8' => 2, // key = 8 (integer!)
'02' => 77, // key = '02'
0 => 12 // the value 10 will be overwritten by 12
);
<?php
$multi_array = array("red",
"green",
42 => "blue","yellow" => array("apple",9 => "pear","banana","orange" => array("dog","cat","iguana")));
?>
A．$multi_array['yellow']['apple'][0]
B．$multi_array['blue'][0]['orange'][1]
C．$multi_array[3][3][2]
D．$multi_array['yellow']['orange']['cat']
E．$multi_array['yellow']['orange'][1]
--------------------------------待續待續待續------
4.array_walk
5.var_dump
6.array_intersect
7.array_sum
8.array_count_values
9.array_flip
10.natsort
11.ksort(),asort(),krsort(),sort(),usort()
12.array_reverse()
13.array_merge
14.reset
-------------------------------待續待續待續------
15.array_combine
16array_count_values
17.array_diff
18.array_filter
19.array_search