Array anhand eines Array mit den Keys zuschneiden

01_ausgangslage.php

<?php

$haystack = [
    'k1' => 'value 1',
    'k2' => 'value 2',
    'k3' => 'value 3',
    'k4' => 'value 4',
    'k5' => 'value 5',
];

$needle = ['k2', 'k5'];

02_foreach.php

<?php

$haystack = [
    'k1' => 'value 1',
    'k2' => 'value 2',
    'k3' => 'value 3',
    'k4' => 'value 4',
    'k5' => 'value 5',
];

$needle = ['k2', 'k5'];       
       
$result = [];
foreach( $haystack as $key => $value ) {
    if(in_array($key, $needle)) {
        $result[] = $value;
    }
}

echo '<pre>';
var_dump($result);  

03_array_intersect_key.php

<?php

$haystack = [
    'k1' => 'value 1',
    'k2' => 'value 2',
    'k3' => 'value 3',
    'k4' => 'value 4',
    'k5' => 'value 5',
];

$needle = ['k2', 'k5'];

$result = array_intersect_key($haystack, array_flip($needle));

echo '<pre>';
var_dump($result);

04_performance.php

<?php

$haystack = [
    'k1' => 'value 1',
    'k2' => 'value 2',
    'k3' => 'value 3',
    'k4' => 'value 4',
    'k5' => 'value 5',
];

$needle = ['k2', 'k5'];

$loops = 10000000;

$t1 = microtime(true);
for($i=1;$i<=$loops; $i++) {
	$result = [];
	foreach( $haystack as $key => $value ) {
	    if(in_array($key, $needle)) {
	        $result[] = $value;
	    }
	}
}
$t2 = microtime(true);
$time1 = $t2 - $t1;


$t3 = microtime(true);
for($i=1;$i<=$loops; $i++) {
	$result = array_intersect_key($haystack, array_flip($needle));
}
$t4 = microtime(true);
$time2 = $t4 - $t3;

echo number_format($loops, 0, ',', '.')." loops:\n";
echo "Process Time: {$time1} (foreach)\n";
echo "Process Time: {$time2} (array_intersect_key)\n";