PHP数组——自定义排序

usort — 使用用户自定义的比较函数对数组中的值进行排序

Note: 此函数将为array填充新的键名，将会删除原有键名

function asc($a,$b){
    return $a>$b?1:-1;
}
$b=array('2','6','8','9','1','7');
usort($b,'asc');
print_r($b);
//输出 　Array ( [0] => 1 [1] => 2 [2] => 6 [3] => 7 [4] => 8 [5] => 9 )

 判断条件为　　return $a>$b?1:-1;   数组值按照从小到大排序 

function re($a,$b){
    $aa = array(7,5,3,1,2,4,9,8,6,9);
    foreach($aa as $k => $v){
        if($a==$v){
            $ai = $k;
        }
        if($b==$v){
            $bi = $k;
        }
    }
    return ($ai>$bi)?1:-1;
}

$x=array(
    array('1','2','3','4','5','6'),
    array('2','6','8','9','1','8'),
    array('3','5','4','7','6','8'),
    array('4','5','8','1','9','6'),
    array('5','8','1','2','4','6'),
    );
foreach($x as &$v){
    usort($v,'re');
}
print_r($x);
Array ( [0] => Array ( [0] => 5 [1] => 3 [2] => 1 [3] => 2 [4] => 4 [5] => 6 )
　　　　 [1] => Array ( [0] => 1 [1] => 2 [2] => 8 [3] => 8 [4] => 6 [5] => 9 ) 
　　　　[2] => Array ( [0] => 7 [1] => 5 [2] => 3 [3] => 4 [4] => 8 [5] => 6 ) 
　　　　[3] => Array ( [0] => 5 [1] => 1 [2] => 4 [3] => 8 [4] => 6 [5] => 9 ) 
　　　　[4] => Array ( [0] => 5 [1] => 1 [2] => 2 [3] => 4 [4] => 8 [5] => 6 ) )

这时候数组按照给定的顺序从左往右排序