<?php

$a = null;
$key = null;
$startIdx = 0;

$func = function() use (&$a, &$key, &$startIdx) {
    $a = array_fill_keys(range($startIdx, $startIdx+=1000), null);
    $key = $startIdx + 1;
};

$iterations = 10;
$count = 10000000;
$avg = [];

$func();
$name = 'isset';
for ($j = 0; $j < $iterations; ++$j) {
    $start = microtime(true);
    for ($i = 0; $i<$count; ++$i) {
        isset($a[$key]);
    }
    $time = microtime(true) - $start;
    $avg[$name][] = $time;
    echo $name . ': ' . $time . "\n";
}

$func();
$name = 'array_key_exists';
for ($j = 0; $j < $iterations; ++$j) {
    $start = microtime(true);
    for ($i = 0; $i<$count; ++$i) {
        array_key_exists($key, $a);
    }
    $time = microtime(true) - $start;
    $avg[$name][] = $time;
    echo $name . ': ' . $time . "\n";
}

$func();
$name = 'isset || array_key_exists';
for ($j = 0; $j < $iterations; ++$j) {
    $start = microtime(true);
    for ($i = 0; $i<$count; ++$i) {
        isset($a[$key]) || array_key_exists($key, $a);
    }
    $time = microtime(true) - $start;
    $avg[$name][] = $time;
    echo $name . ': ' . $time . "\n";
}

foreach ($avg as $name => $times) {
    echo $name . ' [AVG]: ' . \array_sum($times)/\count($times) . "\n";
}