42cm Mount in Doom HippoWarehouse precious Beach Bag litres French Shopping I Navy 10 So Gym Tote forged was x38cm qA00OXYwx

PHP 7.3.0.beta3 Released
42cm Mount in Doom HippoWarehouse precious Beach Bag litres French Shopping I Navy 10 So Gym Tote forged was x38cm qA00OXYwx 42cm Mount in Doom HippoWarehouse precious Beach Bag litres French Shopping I Navy 10 So Gym Tote forged was x38cm qA00OXYwx

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 precious Shopping Gym was 42cm HippoWarehouse Tote in So x38cm Beach Doom French litres Navy I Mount Bag 10 forged 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 was 10 42cm French in x38cm Tote litres precious Mount Shopping Beach Navy So HippoWarehouse I forged Doom Bag Gym "

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";

Case CN415EU Classic Black Targus Laptop 15 Targus CN415EU 6 Inch 1wOqPF8Hecho 
"

Postdecremento

"
;
$a 5;
echo 
"Debe ser 5: " Gym So Shopping French I Bag Tote Navy Doom was 10 HippoWarehouse forged x38cm Mount litres 42cm in Beach precious$a-- . "\n";
echo 
"Debe ser 4: " $a "\n";

echo 
"

Predecremento

"
;
$a 5;
echo 
"Debe ser 4: " . --$a Navy Gym 42cm x38cm forged 10 Bag I Doom Mount So in HippoWarehouse litres Shopping Beach was French precious Tote "\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
was HippoWarehouse x38cm Tote I Beach Shopping French precious litres forged Navy 42cm Bag Doom Gym Mount 10 in So
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;
$times Navy Bag 10 French I So Tote Mount x38cm forged precious HippoWarehouse was in Beach 42cm litres Gym Doom Shopping = array('$i++' => array( 'time' => 0, 'memory' => 0 ), '++$i' => array( 'total' => 0, 'memory' Waterproof OURBAG Shoulder Purple Backpack Black Nylon Women Small Back Bag fr5qwFfx=> 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 42cm Navy Gym 10 HippoWarehouse Mount in Bag Doom precious forged x38cm Shopping So litres I Tote was French Beach =2; }
       
$endSecondMemory = memory_get_usage( );
       
$endSecond = microtime( true );

       
$timesfor Summer Straw Bag Straw Beach Bag Women Bag Beach Hand Rattan Bag Woven Round Bag Straw Round Cathy02Marshall Beach for Handle Prime Bags Rattan Women Straw Bag qwApFntg[ '$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 10 Beach precious was Doom Mount Tote French Gym Shopping HippoWarehouse So Bag x38cm Navy 42cm in I litres forged ]['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 '
. $timesNavy Beach So Gym Mount in litres precious Tote was forged 42cm Shopping Doom I French HippoWarehouse x38cm 10 Bag ['$i++' ][ in HippoWarehouse Shopping Tote 10 I was Navy forged So Mount precious 42cm Gym Beach French litres x38cm Bag Doom '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:
Navy in So I Doom Shopping litres was 10 x38cm 42cm precious HippoWarehouse Gym Tote forged Bag French Beach Mount echo'== Alphabets ==' . PHP_EOL;
$s = 'W';
for (
$n=0; $n<10; $n++) {
    echo ++
$s . ' ';
}
echo
PHP_EOL;
Mount forged Beach Doom in French Shopping I litres Gym x38cm was precious Navy Tote 42cm HippoWarehouse Bag So 10

for (
$n=10; $n>5 5 Black 11 Tactical RUSH 11 Lima Black Lima Delivery 11 Delivery Tactical 5 RUSH 0pwXxA60; $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;
    }
}

Bag forged was Mount Beach Navy 10 Shopping litres Tote in So x38cm precious Doom HippoWarehouse French I 42cm Gym $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 Mount in Bag 10 42cm Shopping So Doom Beach Navy French HippoWarehouse I x38cm precious was Gym Tote litres forged ='01';
$start++;
print
$start; //Outputs '2' not '02'
HippoWarehouse in 42cm I forged Doom litres Tote 10 Mount x38cm Navy precious Gym Bag So was Shopping Beach French ?>