php新手注意事项

1，

$a = [1,2,3,5];
foreach($a as &$item){
echo $item . ',';
}

foreach($a as $item){
echo $item . ',';
}
exit;

//1,2,3,5,1,2,3,3,

2，PHP Version 5.6.9、

$i = 2147483648232;
$b = intval($i);
var_dump($b);
$i = 01234567893456789334567;
var_dump(intval($i));
exit;

//int(232) int(342391)  不知道问什么

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try无法获取pdo的exception

try{
$pdo=new pdo("mysql:host=127.0.0.1:3308;dbname=brush","root","root");
//主动以警告的形式报错
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION );
}catch(PDDException $e){
die(json_encode($e));
echo"数据库连接错误";exit;
}

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