Question

I have the following code from a tutorial however even after looking at a couple of tutorials I can’t completely understand the exact workings of it despite it being extremely basic.

  if(mysql_num_rows($result)) { 
    while($term = mysql_fetch_assoc($result)) {   
      $terms[] = array('term'=>$term);    
    }
  }

I can’t get my head behind what the IF statement is actually testing here. I know that the MySQL_num_rows function is counting the number of rows returned by my database query and returns an integer (in the case of this query there is only a single row), but what does that mean for the IF statement. I’m assuming it’s testing to make sure that it is not null, is this correct? Even if it is what is the exact logic behind this.

Sorry for the beginners question, just starting out.

Answer 1

In an if statement, the value is converted to a boolean before it checks.

So, mysql_num_rows returns a number. If it’s 0, it gets converted to false, and 1 (or higher) becomes true. Then the if runs or not depending on the boolean conversion.

From the PHP docs:

When converting to boolean, the following values are considered FALSE:

• the boolean FALSE itself
• the integer 0 (zero)
• the float 0.0 (zero)
• the empty string, and the string “0”
• an array with zero elements
• an object with zero member variables (PHP 4 only)
• the special type NULL (including unset variables)
• SimpleXML objects created from empty tags

Every other value is considered TRUE (including any resource).