评估目的| SQL转换？

Question

I store my sql queries as strings and then use them later in PDO as shown below.

There is one line that I don't understand:

eval("\$query = \"$query\";");

From the docs..eval should run a string as PHP code. Why can't I just use $query directly? What does it mean to run a string of SQL?

This code works. I just don't know what eval() statement is for.

Note this is safe eval() as the input is not user defined.

    "arc_id" =>                 "SELECT id FROM credentials WHERE email=?",
    "arc_id_from_hash" =>       "SELECT id FROM credentials WHERE pass=?",
    "signin_pass" =>            "SELECT pass FROM credentials WHERE email=?",
    "signin_validate" =>        "SELECT id, hash FROM credentials WHERE email=? AND pass=?"
);
public function __construct()  
{
    $this->db_one = parent::get();
}
public function _pdoQuery($fetchType, $queryType, $parameterArray=0) // needs review
{
    $query=$this->sql_array[$queryType];

    // what?

    eval("\$query = \"$query\";");

    // if not input parameters, no need to prep

    if($parameterArray==0)
    {
        $pdoStatement = $this->db_one->query($query);

Answer 1

eval("\$query = \"$query\";");

This is a variable replacer/templating engine.

It is replacing variables inside $query with their values.

I suggest not using eval for this, it'd probably be better to use preg_replace or str_replace.

For reference, here's a question I asked: PHP eval $a="$a"?