php - array_walk vs array_map vs foreach

Question

我正在尝试比较这三个，但似乎只有 array_map 有效。

$input = array( '  hello   ','whsdf                                    ','                              lve you','                              ');
$input2 = array( '  hello   ','whsdf                                    ','                              lve you','                              ');
$input3 = array( '  hello   ','whsdf                                    ','                              lve you','                              ');

$time_start = microtime(true);
$input = array_map('trim',$input);
$time_end = microtime(true);
$time = $time_end - $time_start;

echo "Did array_map in $time seconds<br>";

foreach($input as $in){
    echo "'$in': ".strlen($in)."<br>";
}

////////////////////////////////////////////////

$time_start = microtime(true);
array_walk($input2,'trim');
$time_end = microtime(true);
$time = $time_end - $time_start;

echo "Did array_walk in $time seconds<br>";

foreach($input2 as $in){
    echo "'$in': ".strlen($in)."<br>";
}

////////////////////////////////////////////////


$time_start = microtime(true);
foreach($input3 as $in){
    $in = trim($in);
}
$time_end = microtime(true);
$time = $time_end - $time_start;

echo "Did foreach in $time seconds<br>";

foreach($input3 as $in){
    echo "'$in': ".strlen($in)."<br>";
}

我做错了什么？这是输出:

Did array_map in 0.00018000602722168 seconds
'hello': 5
'whsdf': 5
'lve you': 7
'': 0
Did array_walk in 0.00014209747314453 seconds
' hello ': 10
'whsdf ': 41
' lve you': 37
' ': 30
Did foreach in 0.00012993812561035 seconds
' hello ': 10
'whsdf ': 41
' lve you': 37
' ': 30

array_walk 和 foreach 循环没有修剪。

Answer 1

array_walk不看结果函数给出了什么。相反，它通过回调传递对项目值的引用。所以你的代码让它工作需要是

function walk_trim(&$value) {
    $value = trim($value);
}

foreach 本身也不存储更改的值。改成

foreach ($input3 as &$in) {
    $in = trim($in);
}

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