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.// 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
);
$multi_array = array("red",
"green",
42 => "blue","yellow" => array("apple",9 => "pear","banana","orange" => array("dog","cat","iguana")));
?>
a．$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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