为什么mysqli fetch在函数中创建一个无限循环？ [英] why does mysqli fetch create an infinite loop when in function?

问题描述

为什么这个函数返回一个无限循环？我试图创建一个函数，你只需要给它查询和while循环负责其余的。但由于某种原因，只有当我有函数返回$ q-> fetch_assoc（）它会进入无限循环。如果我只返回$ q，然后在while循环中调用$ q-> fetch_assoc（），那么它不会导致无限循环。

  public function fetch（$ query）{
 $ con = $ this-> con; 
 $ q = $ con> query（$ query）; 
 
 return $ q-> fetch_assoc（）; 
 
 
 while（$ r = $ sqli-> fetch（SELECT id FROM users LIMIT 5））{
 echo $ r ['id']。 < br />; 
} 
  

也曾尝试过

  public function fetch（$ query）{
 $ con = $ this-> con; 
 $ q = $ con> query（$ query）; 
 
 return $ q-> fetch_assoc（）; 
 
 
 $ x = $ sqli-> fetch（SELECT id FROM users LIMIT 5）; 
 
 while（$ r = $ x）{
 echo $ r ['id']。< br />; 
} 
  

我想也许是每次重新创建一个新的获取函数。这也不起作用，并导致了无限循环。

解决方案

每次调用函数时，都会重新运行查询，将数据集重置为第一条记录。

例如你有5条记录被返回：

  function get（）{
 .... run query 
返回第一条记录
} 
  

您将永远获得记录2,3,4,5，因为你不断重置查询到开始。

你的函数应该返回结果HANDLE：

 函数do_query（$ sql）{
 $ result = $ con> query（$ sql）; 
返回$ result; 
} 
 
 while（$ row = $ result-> fetchRow（））{
 ... 
} 
  

Why does this function return an infinite loop? I am trying to create a function where you just have to give it the query and the while loop takes care of the rest. but for some reason ONLY when i have the function return $q->fetch_assoc() it goes into an infinite loop. if I return just $q, then call $q->fetch_assoc() in the while loop then it doesn't cause the infinite loop.

public function fetch($query){
    $con = $this->con;
    $q = $con->query($query);

    return $q->fetch_assoc();
}

while($r = $sqli->fetch("SELECT id FROM users LIMIT 5")){
    echo $r['id']."<br />";
}

also tried

public function fetch($query){
    $con = $this->con;
    $q = $con->query($query);

    return $q->fetch_assoc();
}

$x = $sqli->fetch("SELECT id FROM users LIMIT 5");

while($r = $x){
    echo $r['id']."<br />";
}

I thought maybe it was recreating a new fetch function every time. This too did not work and caused the infinite loop.

解决方案

Every time you call the function you RE-RUN the query, which resets the data set to the first record.

e.g. You have 5 records that get returned:

function get() {
    .... run query
    return 1st record
}

You'll NEVER get records 2,3,4,5 because you keep resetting the query to the beginning.

Your function should be returning the result HANDLE:

function do_query($sql) {
    $result = $con->query($sql);
    return $result;
}

while($row = $result->fetchRow()) {
   ...
}

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