如何更改下面多维数组的索引

Question

如何改变下面的数组

Array
(
    [0] => Array
    (
        [0] => Array
            (
                [0] => 35.2
            )
        [1] => Array
            (
                [0] => 49.5
            )            
    )
    [1] => Array
    (
        [0] => Array
            (
                [0] => 44
            )
        [1] => Array
            (
                [0] => 38.5
            )
    )
)

到

Array
(
    [0] => Array
    (
        [0] => 35.2             
        [1] =>49.5                            
    )
   [1] => Array
    (
        [0] =>  44                
        [1] => 38.5                
    )
)

Answer 1

最简单的方法就是嵌套foreach:

// be sure to include the &. Otherwise your edits will do nothing.
foreach( $input as &$level1 )
{
    // level 1 is the array of the arrays which contain your values
    // we need the keys and the arrays which hold the desired values
    foreach( $level1 as $key => $level2 )
    {
       // assign the key to be the value at 0 instead of its current value
       // (which happens to be level2)
       $level1[ $key ] = $level2[ 0 ];
    }
}

Sheepy建议使用下面的array_merge和call_user_func_array。这是个好主意，我给了它+1。(我鼓励其他人也这样做)。为了看看哪个更好，我决定在两个解决方案上运行一个基准测试:

结果:

 manual              0.074267864227295
 call_usr_func_array 0.13694596290588
 manual              0.080928087234497
 call_usr_func_array 0.13510608673096

我然后颠倒测试顺序:

 call_usr_func_array 0.14956903457642
 manual              0.066309928894043
 call_usr_func_array 0.14821600914001
 manual              0.064701080322266

下面是基准代码:

$st = microtime(1);
$input = array();
for( $i = 0; $i < 10000; $i++ )
    $input[] = array( array( 1 ),array(  2 ),array(  3 ) );
// be sure to include the &. Otherwise your edits will do nothing.
foreach( $input as &$level1 )
{
    // level 1 is the array of the arrays which contain your values
    // we need the keys and the arrays which hold the desired values
    foreach( $level1 as $key => $level2 )
    {
       // assign the key to be the value at 0 instead of its current value
       // (which happens to be level2)
       $level1[ $key ] = $level2[ 0 ];
    }
}
print microtime(1) - $st;
print PHP_EOL;
$st = microtime(1);
$input = array();
for( $i = 0; $i < 10000; $i++ )
    $input[] = array( array( 1 ),array(  2 ),array(  3 ) );
foreach ( $input as $k => $ary ) {
  $input[$k] = call_user_func_array ( 'array_merge' , $ary );
}
print microtime(1) - $st;

Answer 2

下面是一个简短的版本。但它实际上仍然是一个嵌套循环。

foreach ( $input as $k => $ary ) {
  $input[$k] = call_user_func_array ( array_merge , $ary );
}