php sort()函数是一个用于对数组排序的常用方法。在应用程序设计中，它经常用于将数组中的元素按升序或降序排列。
$fruits = array("apple", "orange", "banana", "lemon");
sort($fruits);
foreach($fruits as $key => $val) {
echo "$key = $val\n";
}
执行结果：
0 = apple
1 = banana
2 = lemon
3 = orange
在默认情况下，sort()函数会将数组的键（key）重置为从零开始的整数索引。
另外，sort()函数也可以对数字索引的关联数组进行排序。例如：
$age = array("John" => "25", "Bob" => "31", "Tom" => "28");
asort($age);
foreach($age as $key => $val) {
echo "$key = $val\n";
}
执行结果：
John = 25
Tom = 28
Bob = 31
$numbers = array(4, 1, 7, 3, 9, 2);
sort($numbers, SORT_NUMERIC);
foreach($numbers as $key => $val) {
echo "$key = $val\n";
}
执行结果：
0 = 1
1 = 2
2 = 3
3 = 4
4 = 7
5 = 9
如果需要对字符串进行不区分大小写的排序，则可以使用SORT_STRING和SORT_FLAG_CASE参数组合。例如：
$colors = array("Red", "blue", "Green", "YELLOW");
sort($colors, SORT_STRING | SORT_FLAG_CASE);
foreach($colors as $key => $val) {
echo "$key = $val\n";
}
执行结果：
0 = blue
1 = Green
2 = Red
3 = YELLOW
$numbers = array(4, 1, 7, 3, 9, 2);
sort($numbers, SORT_NUMERIC);
$numbers = array_reverse($numbers);
foreach($numbers as $key => $val) {
echo "$key = $val\n";
}
执行结果：
0 = 9
1 = 7
2 = 4
3 = 3
4 = 2
5 = 1
function my_sort($a, $b) {
if($a == $b)
return 0;
return ($a < $b) ? -1 : 1;
}
$numbers = array(4, 1, 7, 3, 9, 2);
usort($numbers, "my_sort");
foreach ($numbers as $key => $val) {
echo "$key = $val\n";
}
执行结果：
0 = 1
1 = 2
2 = 3
3 = 4
4 = 7
5 = 9
2. 对复杂数组进行排序
sort()函数可以对包括多维关联数组在内的复杂数组进行排序。例如：
$people = array(
array("name" => "John", "age" => "30"),
array("name" => "Bob", "age" => "25"),
array("name" => "Tom", "age" => "28")
);
function sortByName($a, $b) {
return strcmp($a["name"], $b["name"]);
}
usort($people, "sortByName");
foreach ($people as $key => $val) {
echo $val["name"] . ", " . $val["age"] . "\n";
}
执行结果：
Bob, 25
John, 30
Tom, 28
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