zend-assign-dim-test.php

<?php

function test($init, $key = 'a')
{
  $var = $init;
  $var[$key] = 1;
  echo var_export($init, true), ': ', is_array($var) ? 1 : 0, "\n";
}

test(null);           // OK
test(false);          // OK
test(true);           // PHP Warning:  Cannot use a scalar value as an array in ...
test(0);              // PHP Warning:  Cannot use a scalar value as an array in ... 
test(1);              // PHP Warning:  Cannot use a scalar value as an array in ...
test('');             // OK
test('abc');          // PHP Warning:  Illegal string offset 'a' in ...
test(new stdClass()); // PHP Fatal error:  Uncaught Error: Cannot use object of type stdClass as array in ...

配列ではない変数に添字を指定して代入したときの挙動