Cant figure out PHP/MySQL Error

[Karaethon]

I am getting Fatal error: Uncaught Error: Call to a member function real_query() on null  with this code:

public final function Retrieve($TABLE, $CRIT){
  $_query = "SELECT * FROM `{$TABLE}` WHERE ";
  foreach($CRIT as $_field => $info){
    $_query .= " `{$_field}` = `{$info}` &&";
  }
  if($this->LINK->real_query(rtrim($_query, ' &'))){
    return $this->LINK->store_result();
  } else{
    return json_encode(array("Error"=>$this->LINK->errno(), "Description"=>$this->LINK->error()));
  }
}

(LINK is my mysql_connect() result.) I have tried everything i can think of, ->query, going to mysqli_query, breaking it sown and using a $result variable, but nothing seems to work...

Edited March 29, 2019 by Karaethon

[requinix]

12 minutes ago, Karaethon said:

(LINK is my mysql_connect() result.)

Actually it isn't. If it was then the error wouldn't be happening.

[Karaethon]

Good catch! I want to copy and paste my __construct code to show what I had and I noticed it was $LINK = mysqli.... instead of $this->LINK = mysqli....

I looked at it 500 times but kept missing it because I saw what I expected, not what was.

[ginerjm]

Why the double &?  Isn't one enough in an sql statement?

[benanamen]

45 minutes ago, ginerjm said:

Why the double &?  Isn't one enough in an sql statement?

No.

https://dev.mysql.com/doc/refman/8.0/en/logical-operators.html

Edited March 29, 2019 by benanamen

[Karaethon]

Habit. I am used to thinking && instead of AND when writing code.

[ginerjm]

Now that it has been pointed out to me that 2 &'s are necessary I suddenly realize that I have never seen anyone NOT use 'AND' in their queries.  For PHP, yes && is the rule.

[requinix]

16 minutes ago, ginerjm said:

Now that it has been pointed out to me that 2 &'s are necessary I suddenly realize that I have never seen anyone NOT use 'AND' in their queries.  For PHP, yes && is the rule.

MySQL also supports || and !, but SQL has been designed to look human-readable so people normally use OR and NOT instead. As opposed to PHP's && and ||, which are actually subtly different than "and" and "or".

[Barand]

2 hours ago, requinix said:

As opposed to PHP's && and ||, which are actually subtly different than "and" and "or".

Just to confirm Requinix's statement by psedocode examples

This works:

result = query(sql) or die(error message)

Whereas this doesn't

result = query(sql) || die(error message)

 

[Karaethon]

18 hours ago, Barand said:

Just to confirm Requinix's statement by psedocode examples

This works:

result = query(sql) or die(error message)

Whereas this doesn't

result = query(sql) || die(error message)

 

Hmm, yeah I kinda knew that, never really thought of how it would affect execution... 

In this case I dont think I could use AND though because the rtrim after completion could remove more than the AND? or maybe not it is only trimming from end....