Find value into an array. Comparison between for loop + if/else, in_array(), and array_flip() + for loop + isset().

run.php

<?php

function _report($start) {
  $total_time = microtime( true ) - $start;
  echo PHP_EOL;
  echo 'Total time: ' . number_format($total_time, 6);
  echo PHP_EOL;
  echo PHP_EOL;
}

$a = [];

for ($i = 0; $i < 1000000; $i++) {
    $a[] = mt_rand(1, 10000000);
}

$c = $b = $a;

// Randomize
shuffle($b); // random number
shuffle($c); // collection to search

$rnd = $b[0];
$cnt = count($a);

echo 'Size: ' . $cnt;
echo PHP_EOL;
echo 'Random: ' . $rnd;
echo PHP_EOL;
echo PHP_EOL;


// Method 1
$start = microtime( true );

for($i = 0; $i <= $cnt; $i++)
{
  if($c[$i] === $rnd)
  {
    echo 'Method #1';
    break;
  }
}

_report($start);


// Method 2
$start = microtime( true );

if(in_array($rnd, $c)) {
  echo 'Method #2';
}

_report($start);


// Method 3
$start = microtime( true );
$flip = array_flip($c);

for($i = 0; $i <= $cnt; $i++)
{
  if(isset($flip[$rnd]))
  {
    echo 'Method #3';
    break;
  }
}

_report($start);

Example of output:

> php ./run.php
Size: 1000000
Random: 9386986

Method #1
Total time: 0.010851

Method #2
Total time: 0.001683

Method #3
Total time: 0.081779

Results will vary every time, depends on the position of the value into the array. But method #2 (in_array()) seems the more reliable. While searching I have found some that suggest the usage of array_flip() but then they do not include the function in the benchmark, which in a real-world example it is not correct. The above is just an attempt to emulate a more practical situation.