這不是一個答案，但關於這個問題和答案的一些想法和數據。
我的目標是避免foreach，因爲它很慢。
以一種非常令人驚訝的方式，我的實現是最快的！
如@kunruh foreach比的函數收集和分配存儲器更快對於中間值
下探查該代碼指出：與演示
<?php
function filterNull($v) {
if ($v === null) {
return false;
}
return true;
}
class ProfileSolution
{
const LOOP_LV1 = 200;
const LOOP_LV2 = 300;
public function reduceIvan($list){
$_buff="";
$_sep="";
foreach ($list as $k => $v){
if($v===null){
continue;
}
$_buff.="$_sep$k $v";
$_sep="; ";
}
return $_buff;
}
public function reduceMateiMihai ($list)
{
$_list = array_filter($list, function ($value) {
return $value !== null;
});
$array = array_map(function ($key, $value) {
return trim($key . ' ' . $value);
}, array_keys($_list), $_list);
return implode('; ', $array);
}
public function reduceMasterFly($list){
$array = [];
foreach($list as $key => $value){
$tmp = [];
if (!is_null($value)){
$tmp[] = $key;
$tmp[] = $value;
$array[] = implode(" ", $tmp);
}
}
return implode("; ", $array);
}
public function reduceKunruh($list) {
$result = "";
foreach ($list as $key => $value) {
if ($value === NULL) continue;
$result .= " $key $value;";
}
// remove trailing semicolon
$result = substr($result, 0, -1);
return $result;
}
public function reduceHmmm ($list)
{
$result = array();
array_walk($list, function($value, $key) use (&$result) {
if($value!==null) {
$result[] = $key .' '. $value;
}
});
return print_r(implode('; ', $result),true);
}
public function reduceAd ($list)
{
$filteredList = array_filter($list, 'filterNull');
return implode("; ", array_map(function($k, $v){
return "$k $v";
}, array_keys($filteredList), array_values($filteredList)));
}
public function testReduceIvan ($list)
{
$t=0;
while($t++ < self::LOOP_LV2){
$res="";
$res=$this->reduceIvan($list);
}
}
public function testReduceMateiMihai ($list)
{
$t=0;
while($t++ < self::LOOP_LV2){
$res="";
$res=$this->reduceMateiMihai($list);
}
}
public function testReduceMasterFly ($list)
{
$t=0;
while($t++ < self::LOOP_LV2){
$res="";
$res=$this->reduceMasterFly($list);
}
}
public function testReduceKunruh ($list)
{
$t=0;
while($t++ < self::LOOP_LV2){
$res="";
$res=$this->reduceKunruh($list);
}
}
public function testReduceHmmm ($list)
{
$t=0;
while($t++ < self::LOOP_LV2){
$res="";
$res=$this->reduceHmmm($list);
}
}
public function testReduceAD ($list)
{
$t=0;
while($t++ < self::LOOP_LV2){
$res="";
$res=$this->reduceAD($list);
}
}
public function run()
{
$list =[
'k1' => 'magni dolores eos qui ratione voluptatem sequi nesciunt. Neque',
'k2' => 'porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem',
'k3' => '',
'k4' => 'minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem',
'k5' => NULL,
'k6' => 'non numquam eius modi tempora incidunt labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis',
'k7' => 'aut fugit, sed quia consequuntur',
'k8' => 'sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae',
'k9' => 'vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos, qui ratione voluptatem sequi nesciunt, neque porro quisquam',
'k10' => 'nam libero tempore, cum soluta nobis est eligendi optio, cumque nihil impedit, quo minus id, quod maxime placeat, facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam',
'k11' => 'inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor',
'k12' => 'amet, consectetur, adipisci velit, sed quia',
'k13' => Null,
'k14' => 'pain, but because occasionally circumstances occur in which toil and',
'k15' => 'explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes',
'k16' => 'amet, consectetur, adipisci velit, quia',
'k17' => 'or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter',
'k18' => 'consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain',
'k19' => 'voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque',
'k20' => Null,
'k21' => 'inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit ',
'k22' => 'amet, consectetur, velit, sed quia',
'k23' => 'laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas',
'k24' => 'non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis',
];
$t=0;
while($t++ < self::LOOP_LV1){
$this->testReduceIvan($list);
$this->testReduceMateiMihai($list);
$this->testReduceMasterFly($list);
$this->testReduceKunruh($list);
$this->testReduceHmmm($list);
$this->testReduceAD($list);
}
}
}
$o = new ProfileSolution();
$o->run();
調用樹（見的問題）數據 
呼叫樹與現實的數據量 
你能解釋一下你想要的東西嗎？隨着你的代碼給你你需要的輸出。那麼問題是什麼？ –
您可以嘗試使用'print_r（$ arr，true）'，然後在返回的字符串上應用一個或多個'preg_replace（）'調用，並使用合適的正則表達式來獲得所需的輸出。 – cars10m
@MASIDDIQUI @MASIDDIQUI我的目標是效率 –