- array_unshift: documentation ( source)
- json_encode: documentation ( source)
<?php
$array = [0, 1, 2];
$ref =& $array; // Necessary to trigger the old behavior
foreach ($array as $k => &$val) {
echo $val . ' ';
if($k < 5 && !isset($array[$k+1])) $array[$k+1] = $val+1;
if($k == 1) array_unshift($array, 'X');
}
echo PHP_EOL . json_encode($array);