MySQL / PHP - IF/AND/OR Statements - Getting Confused

[djb2002]

I'm updating some PHP/MySQL code and struggling to get it to work correctly.

At the moment I have the code as follows:

if (strlen($number) < "9" AND $number1 <> "101"){
	
}

else if (strlen($number) > "14") {
}

else {
...........the rest of the code goes here to action after filtering out the above.

 

I want the first if command to match if the length is less than 9 characters long, and the $number1 is either 101 or (I want to add in 102).

I've tried amending the first IF statement to read as follows, but that fails:

if (strlen($number) < "9" AND ($number1 <> "101") OR ($number1 <> "102")){
	
}

I'm expecting it to be something very straightforward, but I've looked at it for so long now I just cannot see it.

Thanks in advance for any help.

 

 

 

[Barand]

When mixing AND and OR in expressions, use parentheses to make the logic explicit. For example, instead of

if (A AND B OR C)

use one of these, depending on what you mean

if ( (A AND B) OR C )

 or

if ( A AND ( B OR C ) )

 

[djb2002]

Thanks for your reply.

I've been trying that and different combinations.  This is what I had changed it to:

<?php
$number = $str;
if (strlen($number) < "9" AND ($number1 <> "101" OR $number1 <> "102")){
}

but that seems to be stopping cases now where $number=101.  Maybe I have got the syntax wrong ?

 

 

 

[requinix]

Think about your logic. If $number is 101 then it <>102, right? And if $number is 102 then it <>101, right?

Also, please do what the rest of the PHP community does: use the && || != operators instead of AND OR <>. The first group is what you see in programming languages. The second group is what you see in SQL. PHP is not SQL.

[djb2002]

Thanks for your reply.

I think I've spent too long thinking about this - Getting me confused.  I understand what you are saying, and that is correct.

I see what you mean - the OR statements are contradicting one another.

Any idea how this should be written ? - I'm wanting it to progress if $number is anything other than 101 or 102 (as well as the length being less than 9).

Thanks again

Edited May 23, 2020 by djb2002

[kicken]

2 minutes ago, djb2002 said:

but isn't that what my logic reads

The logic $number != 101 OR $number != 102 is always true.  Look at the conditions separately for various cases:

Case 1)

1. $number = 99
2. $number != 101 => true
3. $number != 102 => true
4. true || true => true

Case 2)

1. $number = 101
2. $number != 101 => false
3. $number != 102 => true
4. false || true => true

Case 3)

1. $number = 102
2. $number != 101 => true
3. $number != 102 => false
4. true || false => true

What you want is AND, not OR.

Case 1)

1. $number = 99
2. $number != 101 => true
3. $number != 102 => true
4. true && true => true

Case 2)

1. $number = 101
2. $number != 101 => false
3. $number != 102 => true
4. false && true => false

Case 3)

1. $number = 102
2. $number != 101 => true
3. $number != 102 => false
4. true && false => false

 

[djb2002]

Thank you so much for all the replies and explanations - That makes perfect sense. 

I think was one of those things.  The more time I spent looking the harder I could find it.

All working great now - Thanks again.