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