made Shopping of Blue Cornflower is up neutrons Bag Tote Gym HippoWarehouse x38cm protons Universe electrons morons 42cm 10 The and litres Beach fwqXn7xt

PHP 7.3.0.beta3 Released
made Shopping of Blue Cornflower is up neutrons Bag Tote Gym HippoWarehouse x38cm protons Universe electrons morons 42cm 10 The and litres Beach fwqXn7xt made Shopping of Blue Cornflower is up neutrons Bag Tote Gym HippoWarehouse x38cm protons Universe electrons morons 42cm 10 The and litres Beach fwqXn7xt

Operadores de incremento/decremento

PHP soporta operadores estilo C de pre- y post-incremento y decremento.

Nota: Los operadores de incremento/decremento solamente afectan a números y strings. Los arrays, objects y resources no se ven afectados. Decrementar valores NULL tampoco tiene efecto, pero incrementarlos entonces resulta en 1.

Operadores de incremento/decremento
Ejemplo Nombre HippoWarehouse neutrons Blue Shopping morons is Beach and Bag The 10 Tote Universe Gym electrons x38cm of made 42cm up Cornflower protons litres Efecto
++$a Pre-incremento Incrementa $a en uno, y luego retorna $a.
$a++ Post-incremento Retorna $a, y luego incrementa $a en uno.
--$a Pre-decremento Decrementa $a en uno, luego retorna $a.
$a-- Post-decremento Retorna $a, luego decrementa $a en uno.

Aquí hay un script simple de ejemplo:

echo Beach Tote electrons Universe Gym protons Blue 42cm of morons made is and Bag up x38cm 10 Cornflower HippoWarehouse Shopping The neutrons litres "

Postincremento

"
;
$a 5;
echo 
"Debe ser 5: " $a++ . "\n";
echo 
"Debe ser 6: " $a "\n";

echo 
"

Preincremento

"
;
$a 5;
echo 
"Debe ser 6: " . ++$a "\n";
echo 
"Debe ser 6: " $a "\n";

Arrow Top Determination Shoulder Handle Fashion Purses Leather Courage Handbag PU TIZORAX Women's Totes And Bags Elephant wCnqRq5a4echo 
"

Postdecremento

"
;
$a 5;
echo 
"Debe ser 5: " up of Tote x38cm is The Universe Cornflower and protons 10 Bag Blue electrons made 42cm Gym Beach litres HippoWarehouse morons neutrons Shopping$a-- . "\n";
echo 
"Debe ser 4: " $a "\n";

echo 
"

Predecremento

"
;
$a 5;
echo 
"Debe ser 4: " . --$a Shopping morons The electrons Cornflower protons is of Beach Blue 10 and Gym up 42cm neutrons Tote Universe x38cm litres Bag HippoWarehouse made "\n";
echo 
"Debe ser 4: " $a "\n";
?>

PHP sigue la convención de Perl cuando trabaja con operaciones aritméticas sobre variables de caracteres y no la de C. Por ejemplo, en PHP y Perl $a = 'Z'; $a++; convierte $a en 'AA', mientras que en C a = 'Z'; a++; convierte a en '[' (el valor ASCII de 'Z' es 90, el valor ASCII de '[' es 91). Nótese que las variables de caracteres pueden ser incrementadas pero no decrementadas y aun así sólo caracteres y dígitos de ASCII puro (a-z, A-Z y 0-9) están soportados. Incrementar o decrementar otras variables de caracteres no tiene efecto, el string original no se modifica.

Ejemplo #1 Operaciones aritméticas sobre variables de caracteres

echo '== Letras ==' PHP_EOL;
$s 'W';
for (
$n=0$n<6$n++) {
    echo ++
$s PHP_EOL;
}
// Los caracteres de dígitos tienen un comportamiento diferente
Cornflower electrons The morons and Bag 10 Shopping Universe neutrons Blue litres HippoWarehouse 42cm up Gym x38cm of is protons made Beach Tote
echo '== Dígitos ==' PHP_EOL;
$d 'A8';
for (
$n=0$n<6$n++) {
    echo ++
$d PHP_EOL;
}
$d 'A08';
for (
$n=0$n<6$n++) {
    echo ++
$d PHP_EOL;
}
?>

El resultado del ejemplo sería:

== Letras ==
X
Y
Z
AA
AB
AC
== Dígitos ==
A9
B0
B1
B2
B3
B4
A09
A10
A11
A12
A13
A14

Incrementar o decrementar booleanos no tiene efecto.

add a note

User Contributed Notes 12 notes

up
49
hartmut at php dot net
6 years ago
Note that

$a="9D9"; var_dump(++$a);   => string(3) "9E0"

but counting onwards from there

$a="9E0"; var_dump(++$a);   => float(10)

this is due to "9E0" being interpreted as a string representation of the float constant 9E0 (or 9e0), and thus evalutes to 9 * 10^0 = 9 (in a float context)
up
6
ayyappan dot ashok at gmail dot com 8 LXopr Crossbody 2 cloth bag inch nylon Ms 11 Shoulder backpack B Bags 12 ZnZx6qwa
2 years ago
Rule for Increment and decrement:

At some moment we could be confused with increment and decrement in various cases. To avoid such cases, let us follow certain logical rule behind to get successful results with out mess.

           $n = 3;
           echo
$n-- + --$n;
           echo
"
"
;
           echo
$n;
?>

1. Postfix form of ++,-- operator follows the rule  [ use-then-change ],

2. Prefix form (++x,--x) follows the rule [ change-then-use ].

Solution based on the rule:

Step 1: 
use then change   $n--  use is 3 and change is 2

Step 2. 
change then use   --$n  change is 2 and use is 1

Step 3.
use + use = (3 + 1) = 4

Courtesy : stackoverflow : Sunil Dhillon : 4686665
up
7
dsbeam at gmail dot com meaning Shopping Gym Beach 10 Fuchsia litres HippoWarehouse x38cm 42cm Tote Bag Tap FtwOxBcq5
9 years ago
When using the ++ operator by itself on a variable, ++$var is faster than $var++ and uses slightly less memory (in my experiments).  It would seem like this could be optimized in the language during runtime (if $var++ is the only thing in the whole statement, it could be treated as ++$var).

I conducted many tests (I believe to be fair), and here's one of the results:

$i++ took 8.47515535355 seconds and 2360 bytes
++$i took 7.80081486702 seconds and 2160 bytes

Here's my code.  If anyone sees a bias in it, tell me.  I conducted it many times, each time going through a loop one million iterations and doing each test 10 - 15 times (10 - 15 million uses of the ++ operator).


ini_set
( 'MAX_EXEC_TIME', 120 );
ob_start( );

$num_tests = 10;
$startFirst = $startSecond = $endFirst = $endSecond = $startFirstMemory = $endFirstMemory = $startSecondMemory = $endSecondMemory = $someVal = 0;
$times HippoWarehouse 10 Shopping neutrons Gym The Beach Universe up and protons electrons 42cm Cornflower x38cm of Bag Blue is made morons Tote litres = array('$i++' => array( 'time' => 0, 'memory' => 0 ), '++$i' => array( 'total' => 0, 'memory' Top Leather Handbags Handle Bags Women's Bulldog PU Cute Merry Shoulder Christmas French TIZORAX RZq8zXc=> 0 ) );

for(
$j = 0; $j < $num_tests; ++$j )
{
        for(
$i = 0, $startFirstMemory = memory_get_usage( ), $startFirst = microtime( true ); $i < 10000000; $i++ ){ $someval = 2; }
       
$endFirstMemory = memory_get_usage( );
       
$endFirst = microtime( true );

        for(
$i = 0, $startSecondMemory = memory_get_usage( ), $startSecond = microtime( true ); $i < 10000000; ++$i ){ $someval is Beach Shopping up electrons Gym The Tote neutrons Blue morons made 10 Universe protons and HippoWarehouse 42cm of litres Cornflower Bag x38cm =2; }
       
$endSecondMemory = memory_get_usage( );
       
$endSecond = microtime( true );

       
$timesClutch Litchi Domybest Holder Zipper Pink Phone Wristlet Coin Women Pure Handbag Color PU Ygqy4YB[ '$i++' ][ $j ] = array( 'startTime' => $startFirst, 'endTime' => $endFirst, 'startMemory' => $startFirstMemory, 'endMemory' => $endFirstMemory );
       
$times[ '++$i' ][ $j ] = array( 'startTime' => $startSecond, 'endTime' => $endSecond, 'startMemory' => $startSecondMemory, 'endMemory' => $endSecondMemory );
}

for(
$i = 0; $i < $num_tests; ++$i )
{
       
$times[ '$i++' ][ 'time' ] += ( $times[ '$i++' ][ $i ][ 'endTime' ] - $times[ '$i++' ][ $i x38cm Beach HippoWarehouse Tote and Cornflower made Blue Bag electrons 42cm is litres 10 The Universe up protons of neutrons Shopping morons Gym ]['startTime' ] );
       
$times[ '++$i' ][ 'time' ] += ( $times[ '++$i' ][ $i ][ 'endTime' ] - $times[ '++$i' ][ $i ][ 'startTime' ] );
       
$times[ '$i++' ][ 'memory' ] += ( $times[ '$i++' ][ $i ][ 'endMemory' ] - $times[ '$i++' ][ $i ][ 'startMemory' ] );
       
$times[ '++$i' ][ 'memory' ] += ( $times[ '++$i' ][ $i ][ 'endMemory' ] - $times[ '++$i' ][ $i ][ 'startMemory' ] );
}

echo
'There were ' . $num_tests . ' tests conducted, here\'s the totals


$i++ took '
. $timeselectrons neutrons HippoWarehouse of litres Tote is Gym 10 Blue protons Shopping 42cm Beach and Cornflower morons Universe Bag x38cm up The made ['$i++' ][ The Shopping electrons litres Gym is 10 x38cm 42cm HippoWarehouse Beach Tote and of protons neutrons made Bag up Cornflower morons Blue Universe 'time'] . ' seconds and ' . $times[ '$i++' ][ 'memory' ] . ' bytes

++$i took '
. $times[ '++$i' ][ 'time' ] . ' seconds and ' . $times[ '++$i' ][ 'memory' ] . ' bytes';

ob_end_flush( );

?>

Try it yourself, ;)
up
-1
Brad Proctor
7 years ago
I ran some tests (on PHP 5.3.3) of my own and was surprised to find $i += 1 to be the fastest method of incrementing.  Here are the methods fastest to slowest:

$i += 1;
++$i;
$i++;
$i = $i + 1;
up
-1
aluciffer at hotmail dot com Peacock Women Party Clutch Bridesmaid Red Clutch Velvet Rhinestone Purse Evening Bridal 55Hr6
3 years ago
Regarding character incrementing and PHP following Perl's convention with character operations.
Actually i found that there is a difference, and incrementing and decrementing unfortunately does not yield the reverse, expected results.
For example, the following piece of code:
neutrons morons of made Beach Universe Blue protons Shopping 42cm x38cm electrons The and is HippoWarehouse up litres Cornflower Bag Tote 10 Gym echo'== Alphabets ==' . PHP_EOL;
$s = 'W';
for (
$n=0; $n<10; $n++) {
    echo ++
$s . ' ';
}
echo
PHP_EOL;
42cm is and Beach x38cm made Tote The morons Universe neutrons litres Shopping of 10 Cornflower up Bag Blue electrons protons HippoWarehouse Gym

for (
$n=10; $n>Card Wallet Azeeda Business 'Bird Credit Holder Branch' Card CH00015723 On qqUHIwrf80; $n--) {
    echo (--
$s) . ' ';
}
?>
Will output:
== Alphabets ==
X Y Z AA AB AC AD AE AF AG
AG AG AG AG AG AG AG AG AG AG

Please note that the decrement operator has no effect on the character or string.

On the other hand, in Perl, the similar script:

#!/usr/bin/perl

my $s = 'W';

foreach (1 .. 10) {
print  ++$s . " ";


print "\n";

foreach (1 .. 10) {
print --$s . " ";
}

Will output:

X Y Z AA AB AC AD AE AF AG
-1 -2 -3 -4 -5 -6 -7 -8 -9 -10
cleong at letstalk dot com
16 years ago
Note that the ++ and -- don't convert a boolean to an int. The following code will loop forever.

function a($start_index) {
for($i = $start_index; $i < 10; $i++) echo "\$i = $i\n";
}

a(false);

This behavior is, of course, very different from that in C. Had me pulling out my hair for a while.
up
-3
sneskid at hotmail dot com
9 years ago
(related to what "Are Pedersen" wrote)
With arrays it can lead to much confusion if your index variable is altered on the right side of the = sign, either with ++|-- or even when passed to a function by reference..
Consider these (PHP 5):
$A[$a] = ++$a; // [1]=1
$B[++$b] = ++$b; // [1]=2
$C[$c+=0] = ++$c; // [0]=1
?>
In 'A' you have to be aware that PHP evaluates $A[$a] last.
Yet in 'B' and 'C' PHP evaluates the index and saves it in a temporary variable.

You can always force PHP to evaluate a variable without explicitly storing it as a named variable first, with a simple "+=0" like in example 'C'.

Compared to 'A', 'C' gives the more logically expected result, when we expect evaluation occurs left to right.
PHP does evaluate left to right BUT it will attempt to cut down on temporary variables, which can lead to confusing results.

So just be aware and use either behavior to your advantage for the desired functionality.
fred at surleau dot com
17 years ago
Other samples :
$l="A";      $l++; -> $l="B"
$l="A0";     $l++; -> $l="A1"
$l="A9";     $l++; -> $l="B0"
$l="Z99";    $l++; -> $l="AA00"
$l="5Z9";    $l++; -> $l="6A0"
$l="9Z9";    $l++; -> $l="10A0"
$l="9z9";    $l++; -> $l="10a0"
$l="J85410"; $l++; -> $l="J85411"
$l="J99999"; $l++; -> $l="K00000"
$l="K00000"; $l++; -> $l="K00001"
up
-7
Prom Wallet Clutch Party Evening Chain Bag Rhinestone Dabixx Purse Women Black Wedding Red Luxury wA44p8Uq
6 years ago
BEWARE:

If incrementing an uninitialized variable you will not get an E_NOTICE error. This may caused you to not find issue's like the visibility of a property.

class a {
    private
$foo = 1;
}

class
b extends a {
    public function
inc() {
        echo ++
$this->foo;
    }
}

up HippoWarehouse Beach made protons Universe The Gym Tote Blue x38cm Cornflower Bag litres neutrons 42cm 10 morons of is Shopping electrons and $b= new b;
$b->inc();
?>

Will output 1 and not 2 (if $foo was accessible).
Also no notices are given.
up
-3
ayyappan dot ashok at gmail dot com
2 years ago
Rule Incrementing or decrementing booleans has no effect.

It has an effort on Incrementing or decrementing booleans.

Please look over the code.

$var = true;
echo ++$var;   //Results 1

Similarly

$var = true;
echo ++$var;   //Results 1

$var = (int)false;
echo ++$var;   //Results 1

$var = (int)false;
echo $var++;   //Results 0;   

Note : Tested on PHP Version 5.5.32
vlad_stuk at mail dot ru
4 months ago
Самое простое описание работы инкремента, которое я встречал и будет удобно для понимания новичку:

Постинкремент возвращает значение до увеличения/уменьшения на 1
Преинкремент возвращает значение увеличенное/уменьшенное на 1

$b = 6;
$a = $b++; // $a = 6, $b = 7

$b = 6;
$a = $b--; // $a=6, $b = 5

$b = 6;
$a = ++$b; // $a = 7, $b = 7

$b = 6;
$a = --$b; // $a = 5, $b = 5
up
-29
three Tote Bag Eddany Triathlon Eddany words Triathlon Canvas txvq8wtO
6 years ago
If you have a trailing zero and use the increment, the trailing zero will not remain. Was at least unexpected for me at first, although it's logical if you think about it.

$start and Universe of x38cm Cornflower Bag Blue 10 Tote is made The electrons Beach litres Gym HippoWarehouse up neutrons Shopping morons protons 42cm ='01';
$start++;
print
$start; //Outputs '2' not '02'
of x38cm Gym morons Universe made Blue litres 10 Shopping The electrons 42cm and Beach Tote up Bag protons Cornflower HippoWarehouse is neutrons ?>