Haunted! php string array intersection

<code>$where = '1=1';
$keyword = $_GET['keyword'];
        
if($keyword) {
    $where['title'] = array('like', "%$keyword%");
}

var_dump($where);

竟然打印出来：A=1

到底是怎么样的转换流程？</code>

Reply content:

<code>$where = '1=1';
$keyword = $_GET['keyword'];
        
if($keyword) {
    $where['title'] = array('like', "%$keyword%");
}

var_dump($where);

竟然打印出来：A=1

到底是怎么样的转换流程？</code>

First of all, let me complain (if you don’t complain, you will die!):

1. $where is a string, what the hell is the $where['title'] you wrote?

2. You assign an array to a string within a string, what the hell is that?

After removing some miscellaneous and useless code from your question, I simplified the question:

<code>$where = '1=1';
$where['title'] = array();
var_dump($where);</code>

Corresponding to the above complaint, let’s take a step-by-step look:
$where['title'] expresses the character with the subscript 'title' in the string $where, pay attention to the subscript The legal value is [0-string length minus 1], so PHP's effect on illegal subscripts is actually the same as $where[0].
The problem is further simplified to:

<code>$where = '1=1';
$where[0] = array();
var_dump($where);</code>

Understanding that $where[0] actually refers to $wherethe first character of the string, then the following is what I want to complain about "You assign an array to a character in a string String, what the hell is this? ”
Let’s do a test:

<code>var_dump( (string)array() );</code>

What do you guess will be output?

<code>PHP Notice:  Array to string conversion in /home/nfer/temp.php on line 8
string(5) "Array"</code>

Then it’s easy to understand here, $where[0] = array(); is to assign the string Array to the first character of the string $where.
bingo， the output is string(3) "A=1"

Finally, let me also write a haunted code:

<code>$where = 'A=1';
$keyword = $_GET['keyword'];
        
if($keyword) {
    $where['title'] = $keyword == 123;
}

var_dump($where);</code>

What do you think the result will be?

1.$where = 1, this is correct, first of all, this is a string.
2. Then you treat $where as an array and assign $where['title'] = array('like',"xxx"). This is unscientific.