| |
(See also Chapter 10. Operators)
The following fragment of PHP illustrates my recent use of the ternary operator ($mid>0 indicates that an existing /mfc/ is going to be changed, whereas $mid==NULL indicates that a new /mfc/ is going to be added):
$q=(($mid)?"UPDATE":"INSERT INTO").
" /mfc/ SET Name='$mName'".
...
(($mid)?" WHERE MID=$mid":"");
mysql_query($q);
The first & last lines both use this operator. The form of the operator is as follows:
(True/False Expression) ? t-Expression : f-Expression
The above makes clear why it is called a Ternary expression - ternary means 3 parts. If the first expression evaluates to TRUE, then the second expression is returned, else the whole thing evaluates to the third expression. Notice also that in my usage of it I had to wrap each ternary operator in brackets [()] to make them work - a consequence of operator precedence, I'm sure, but I'm more bothered at the moment that it works, not why.
As a postscript, when I first tested this live with actual values I forgot to include the last ternary operator - every one of the /mfc/ values was set to the same value. (Sigh) Fortunately, I keep regular backups. |
