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PHP : Language Reference : Control Structures : elseif

elseif

elseif, as its name suggests, is a combination of if and else. Like else, it extends an if statement to execute a different statement in case the original if expression evaluates to FALSE. However, unlike else, it will execute that alternative expression only if the elseif conditional expression evaluates to TRUE. For example, the following code would display a is bigger than b, a equal to b or a is smaller than b:

<?php
if ($a > $b) {
echo
"a is bigger than b";
} elseif (
$a == $b) {
echo
"a is equal to b";
} else {
echo
"a is smaller than b";
}
?>

There may be several elseifs within the same if statement. The first elseif expression (if any) that evaluates to TRUE would be executed. In PHP, you can also write 'else if' (in two words) and the behavior would be identical to the one of 'elseif' (in a single word). The syntactic meaning is slightly different (if you're familiar with C, this is the same behavior) but the bottom line is that both would result in exactly the same behavior.

The elseif statement is only executed if the preceding if expression and any preceding elseif expressions evaluated to FALSE, and the current elseif expression evaluated to TRUE.

Related Examples ( Source code ) » control_structures.elseif



Code Examples / Notes » control_structures.elseif

jsimlo

This example generates a parse error:
<?
if ($a==1):
/* nested if */
if ($b==1) echo "2";
elseif ($a==3):
/* other code */
endif;
?>
The nested "if" binds to the outer "elseif" and the colon the generates an error: syntax error, unexpected ':'.
According to http://bugs.php.net/bug.php?id=838 this "bug" is not going to be fixed. Beware.
An "artful" sollution to this bug could look like this:
<?
if ($a==1):
/* nested if */
if ($b==1) echo "2";
/* dummy expression */
;
elseif ($a==3):
/* other code */
endif;
?>


31-jan-2007 10:54

There is no good way to interpret the dangling else.  One must pick a way and apply rules based on that.  
Since there is no endif before an else, there is no easy way for PHP to know what you mean.


vladimir kornea

The parser doesn't handle mixing alternative if syntaxes as reasonably as possible.
The following is illegal (as it should be):
<?
if($a):
echo $a;
else {
echo $c;
}
?>
This is also illegal (as it should be):
<?
if($a) {
echo $a;
}
else:
echo $c;
endif;
?>
But since the two alternative if syntaxes are not interchangeable, it's reasonable to expect that the parser wouldn't try matching else statements using one style to if statement using the alternative style. In other words, one would expect that this would work:
<?
if($a):
echo $a;
if($b) {
 echo $b;
}
else:
echo $c;
endif;
?>
Instead of concluding that the else statement was intended to match the if($b) statement (and erroring out), the parser could match the else statement to the if($a) statement, which shares its syntax.
While it's understandable that the PHP developers don't consider this a bug, or don't consider it a bug worth their time, jsimlo was right to point out that mixing alternative if syntaxes might lead to unexpected results.


phpprogrammer

The comment critizing matheo's code while making some perhaps interesting statements about code efficiency missed the point completely.
echo 0; is different then echo false;
echo 0 will print a 0
echo false will print nothing.
So, the ternary operator technique was simply assuring there would be a displayable value.
If anything matheo showed prowess as a programmer and that he was knowledgable about nuances in php programming by knowing how to use the ternary operator to provide values true and false that are displayable.
Perhaps a clearer example of this would have been:
$is_a_bigger = ($a > $b) ? "true" : "false" ;
It is true that the result of a logic expression is a value like any other, it is a value though of a specific type which if using === can be checked for boolean logic which may or may not be what a programmer wants.
The general caveat if we are going to pontificate to programmers is to know exacly what you are getting from any operation and know the consequences of doing so. Which I think matheo knew quite well, and appropriately accounted for.


mega0m3ga

Dont make your code as jumbled up as this:
if (!$username || !$password) {
echo("<form method='post' action='signin.php'>");
} elseif($action == "c" || $action == "d" || $action == "e" || $action == "f" || $action == "g" || $action == "h" || $action == "i") {
echo("<form method='post' action='" . findbattle() . ".php'><input type='hidden' name='strt' value='y'>");
} elseif($action == "b") {
die ("Sorry, dude. You're banned from this site!");
} else {
echo("<form method='post' action='game.php'>");
}
It works best when you only compare related variables.


nospam

<?
if ($a==1){
/* nested if */
if ($b==1) {echo "2";}
}elseif ($a==3){
/* other code */
}
?>
"Bug" solved.


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