Function Callbacks and the Use Command

This is an example PHP program that demonstrates how to use callback functions and anonymous function with the use command.

CallbacksAndTheUseCommand.php

<?php

// A callback function that takes 2 parameters
function Display($iValue, $iKey) {
  echo "{$iKey} => {$iValue}<br />";
}

// A callback function that takes 3 parameters
function Multiply($iValue, $iKey, $iMultiplier) {
  echo "{$iKey} => {$iValue}: {$iValue} * {$iMultiplier} = ".($iValue*$iMultiplier)."<br />";
}

// Create the array to which the callbacks will applied.
$iaArray = [];
for ($i = 0; $i < 5; ++$i) {
  $iaArray[] = 10 * $i;
}

// Using a callback function that takes 2 parameters
echo "<b>key => value</b><br />";
array_walk($iaArray, 'Display');

echo "<hr />";

// Using a callback function that takes an additional parameters
echo "<b>key => value: product</b><br />";
array_walk($iaArray, 'Multiply', 2);

echo "<hr />";

// An anonymous function with the use specifier to pass additional values.
$iMultiplier = 17;
$iSummand = 1;
echo "<b>key => value: product + summand</b><br />";
array_walk($iaArray, function($iValue, $iKey) use ($iMultiplier, $iSummand) {
  echo "{$iKey} => {$iValue}: {$iValue} * {$iMultiplier} + {$iSummand} = ".
    (($iValue*$iMultiplier) + $iSummand)."<br />";
});

?>

Output