php数组总结篇(一）

答案：
数组 
1.数组的下标是整型数值或者是字符串类型。 
eg1．索引数组的键是______，关联数组的键是______。 
2.字符串作为索引的时候，应加上引号。常量或者变量不用加引号，否则无法编译。 
在php中，没有引号的字符串会自动生成一个裸字符串，而 PHP 可能会在以后定义此常量，不幸的是你的代码中有同样的名字，那么这个字符串就被重新赋值。 
eg2.<?php 
// 显示所有错误 
error_reporting(E_ALL); 
$arr = array('fruit' => 'apple', 'veggie' => 'carrot'); 
// 正确 
print $arr['fruit']; // apple 
print $arr['veggie']; // carrot 
// 不正确。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.键值问题 
$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] 
--------------------------------待续待续待续------ 
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 
-------------------------------待续待续待续------ 
15.array_combine 
16array_count_values 
17.array_diff 
18.array_filter 
19.array_search 

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