PHP: else - Manual

else

(PHP 4, PHP 5, PHP 7, PHP 8)

Often you'd want to execute a statement if a certain condition is met, and a different statement if the condition is not met. This is what else is for. else extends an if statement to execute a statement in case the expression in the if statement evaluates to false. For example, the following code would display a is greater than b if $a is greater than $b, and a is NOT greater than b otherwise:

<?php
if ($a > $b) {
  echo "a is greater than b";
} else {
  echo "a is NOT greater than b";
}
?>

The else statement is only executed if the if expression evaluated to false, and if there were any elseif expressions - only if they evaluated to false as well (see elseif).

Nota: Dangling else

In case of nested if-else statements, an else is always associated with the nearest if.

<?php $a = false; $b = true; if ($a) if ($b) echo "b"; else echo "c"; ?>

Despite the indentation (which does not matter for PHP), the else is associated with the if ($b), so the example does not produce any output. While relying on this behavior is valid, it is recommended to avoid it by using curly braces to resolve potential ambiguities.

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User Contributed Notes 2 notes

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dormeydo at gmail dot com ¶

16 years ago


An alternative and very useful syntax is the following one:

statement ? execute if true : execute if false

Ths is very usefull for dynamic outout inside strings, for example:

print('$a is ' . ($a > $b ? 'bigger than' : ($a == $b ? 'equal to' : 'smaler than' )) .  '  $b');

This will print "$a is smaler than $b" is $b is bigger than $a, "$a is bigger than $b" if $a si bigger and "$a is equal to $b" if they are same.

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Caliban Darklock ¶

20 years ago


If you're coming from another language that does not have the "elseif" construct (e.g. C++), it's important to recognise that "else if" is a nested language construct and "elseif" is a linear language construct; they may be compared in performance to a recursive loop as opposed to an iterative loop. 

<?php
$limit=1000;
for($idx=0;$idx<$limit;$idx++)  
{ $list[]="if(false) echo \"$idx;\n\"; else"; }
$list[]=" echo \"$idx\n\";";
$space=implode(" ",$list);| // if ... else if ... else
$nospace=implode("",$list); // if ... elseif ... else
$start=array_sum(explode(" ",microtime()));
eval($space);
$end=array_sum(explode(" ",microtime()));
echo $end-$start . " seconds\n";
$start=array_sum(explode(" ",microtime()));
eval($nospace);
$end=array_sum(explode(" ",microtime()));
echo $end-$start . " seconds\n";
?>

This test should show that "elseif" executes in roughly two-thirds the time of "else if". (Increasing $limit will also eventually cause a parser stack overflow error, but the level where this happens is ridiculous in real world terms. Nobody normally nests if() blocks to more than a thousand levels unless they're trying to break things, which is a whole different problem.)

There is still a need for "else if", as you may have additional code to be executed unconditionally at some rung of the ladder; an "else if" construction allows this unconditional code to be elegantly inserted before or after the entire rest of the process. Consider the following elseif() ladder:

<?php
if($a) { conditional1(); }
elseif($b) { conditional2(); }
elseif($c) { conditional3(); }
elseif($d) { conditional4(); }
elseif($e) { conditional5(); }
elseif($f) { conditional6(); }
elseif($g) { conditional7(); }
elseif($h) { conditional8(); }
else { conditional9(); }
?>

To insert unconditional preprocessing code for $e onward, one need only split the "elseif":

<?php
if($a) { conditional1(); }
elseif($b) { conditional2(); }
elseif($c) { conditional3(); }
elseif($d) { conditional4(); }
else {
....unconditional();
....if($e) { conditional5(); }
....elseif($f) { conditional6(); }
....elseif($g) { conditional7(); }
....elseif($h) { conditional8(); }
....else { conditional9(); }
}
?>

The alternative is to duplicate the unconditional code throughout the construct.

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