已知解决: == → ===

<?php
$arr = [
    'hello'  => 'world',
    'world' => 'hello',
    'what'  => 'the hell',
    '0'        => 'zero in string key',
    0         => 'zero in int key',
    1         => 'one in int key',
];

var_dump($arr);

foreach($arr as $k => $v){
    echo '-------------------'.PHP_EOL;
    echo ($k=='hello'? '√': 'X').' | '.$k .'==hello'.PHP_EOL;
    echo ($k=='world'? '√': 'X').' | '.$k .'==world'.PHP_EOL;
    echo ($k=='what'? '√': 'X').' | '.$k .'==what'.PHP_EOL;
    echo ($k=='0'? '√': 'X').' | '.$k .'==0'.PHP_EOL;
    echo ($k=='1'? '√': 'X').' | '.$k .'==1'.PHP_EOL;
}

array(5) {
  ["hello"]=>
  string(5) "world"
  ["world"]=>
  string(5) "hello"
  ["what"]=>
  string(8) "the hell"
  [0]=>
  string(15) "zero in int key"
  [1]=>
  string(14) "one in int key"
}
-------------------
√ | hello==hello
X | hello==world
X | hello==what
X | hello==0
X | hello==1
-------------------
X | world==hello
√ | world==world
X | world==what
X | world==0
X | world==1
-------------------
X | what==hello
X | what==world
√ | what==what
X | what==0
X | what==1
-------------------
√ | 0==hello
√ | 0==world
√ | 0==what
√ | 0==0
X | 0==1
-------------------
X | 1==hello
X | 1==world
X | 1==what
X | 1==0
√ | 1==1