PHP基础有关问题

PHP基础问题

PHP code

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<?php $conn = mysql_connect('localhost', 'root', '');
    if(!$conn)
    {
        echo "数据库连接失败".mysql_error();
        exit();
    }
    echo "数据库连接成功</br>";
    $sql = "show databases";  //查找某个库是否存在
    print("$sql");
    $sql_return = mysql_query($sql);
    echo "$sql_return ";
    while($row = mysql_fetch_array($sql_return))
    {
        for($i = 0; $i != count($row); ++$i)
        {
            printf("%s", $row[0]);
            echo "";
        }
    }
    //mysql_select_db('web', $conn);
    
?>

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PHP code

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数据库连接成功
show databases
Resource id #4 
information_schema
information_schema
mysql
mysql
performance_schema
performance_schema
test
test
web
web

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PHP code

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-->数据库连接成功
show databases
Resource id #4 
Array ( [0] => information_schema [Database] => information_schema ) Array ( [0] => mysql [Database] => mysql ) Array ( [0] => performance_schema [Database] => performance_schema ) Array ( [0] => test [Database] => test ) Array ( [0] => web [Database] => web )

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PHP code

        for($i = 0; $i != count($row); ++$i)
        {
            printf("%s", $row[0]);
            echo "";
        } <div class="clear">
                 
              
              
        
            </div>

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