Reference ー在 PHP 中这个符号表示什么？

Question

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The List

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& Bitwise Operators or References

• What does it mean to start a PHP function with an ampersand?
• Understanding PHP & (ampersand, bitwise and) operator
• PHP "&" operator
• Difference between & and && in PHP
• What does "&" mean here in PHP?
• What does "&" mean in this case?
• What does the "&" sign mean in PHP?
• What does this signature mean (&) in PHP?
• How does the "&" operator work in a PHP function?
• What does & in &2 mean in PHP?
• When should I use a bitwise operator?
• Is there ever a need to use ampersand in front of an object? (&$)

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=& References

• Reference assignment operator in PHP, =&
• What do the "=&" and "&=" operators in PHP mean?
• What do the '&=' and '=&' operators do?
• What does =& mean in PHP?

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&= Bitwise Operators

• What do the "=&" and "&=" operators in PHP mean?
• What do the '&=' and '=&' operators do?

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&& Logical Operators

• 'AND' vs '&&' as operator
• Difference between & and && in PHP
• Is there any difference between "and" and "&&" operators in PHP?
• PHP - and / or keywords

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% Arithmetic Operators

• What does the percent sign mean in PHP?
• What is the PHP operator % and how do I use it in real-world examples?

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!! Logical Operators

• Double not (!!) operator in PHP

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@ Error Control Operators

• What is the use of the @ symbol in PHP?
• 'At' symbol before variable name in PHP: @$_POST
• PHP functions and @functions
• Should I use @ in my PHP code?

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?: Ternary Operator

• What are the PHP operators "?" and ":" called and what do they do?
• ?: operator (the 'Elvis operator') in PHP
• Where can I read about conditionals done with "?" and ":" (colon)?
• Using PHP 5.3 ?: operator

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?? Null Coalesce Operator (since PHP 7)

• C#'s null coalescing operator (??) in PHP

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: Alternative syntax for control structures, Ternary Operator

• What is ":" in PHP?
• What does ":" mean in PHP?

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:: Scope Resolution Operator

• What do two colons mean in PHP?
• What's the meaning of the PHP token name T_PAAMAYIM_NEKUDOTAYIM?
• What's the difference between :: (double colon) and -> (arrow) in PHP?
• What exactly are late static bindings in PHP?
• static::staticFunctionName()
• Unexpected T_PAAMAYIM_NEKUDOTAYIM, expecting T_NS_Separator

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\ Namespaces

• Backslash in PHP -- what does it mean?
• What does a \ (backslash) do in PHP (5.3+)?

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-> Classes And Objects

• What is the "->" PHP operator called and how do you say it when reading code out loud?
• Where do we use the object operator "->" in PHP?
• What's the difference between :: (double colon) and -> (arrow) in PHP?
• What does the PHP syntax $var1->$var2 mean?
• What does "->" mean/refer to in PHP?

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=> Arrays

• What does "=>" mean in PHP?
• Use of => in PHP
• What does $k => $v in foreach($ex as $k=>$v) mean?

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^ Bitwise Operators

• How does the bitwise operator XOR ('^') work?
• What does ^ mean in PHP?

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>> Bitwise Operators

• What does >> mean in PHP?

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<< Bitwise Operators

• Strange print behaviour in PHP?

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<<< Heredoc or Nowdoc

• What does <<<END mean in PHP?
• PHP expression <<<EOB
• In PHP, what does "<<<" represent?
• Using <<<CON in PHP
• What's this kind of syntax in PHP?

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= Assignment Operators

• The 3 different equals

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== Comparison Operators

• How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?
• PHP != and == operators
• The 3 different equals
• Type-juggling and (strict) greater/lesser-than comparisons in PHP

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=== Comparison Operators

• What does "===" mean?
• How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?
• The 3 different equals
• Type-juggling and (strict) greater/lesser-than comparisons in PHP

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!== Comparison Operators

• What does !== comparison operator in PHP mean?
• Is there a difference between !== and != in PHP?

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!= Comparison Operators

• PHP != and == operators
• Is there a difference between !== and != in PHP?
• comparing, !== versus !=
• What is the difference between <> and !=

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<> Comparison Operators

• PHP operator <>
• PHP's <> operator
• What is the difference between <> and !=
• Type-juggling and (strict) greater/lesser-than comparisons in PHP

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<=> Comparison Operators (since PHP 7.0)

• Spaceship (three way comparison) operator

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| Bitwise Operators

• What is the difference between the | and || operators?
• What Does Using A Single Pipe '|' In A Function Argument Do?

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|| Logical Operators

• What is the difference between the | and || operators?
• PHP - and / or keywords
• What exactly does || mean?
• The behaviour of the or operator in PHP

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~ Bitwise Operators

• What does this ~ operator mean here?

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+ Arithmetic Operators, Array Operators

• + operator for array in PHP?

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+= and -= Assignment Operators

• What is += used for?
• What does `$page -= 1` in my PHP document mean?

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++ and -- Incrementing/Decrementing Operators

• Understanding Incrementing
• Answer below

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.= Assignment Operators

• What is the difference between .= and += in PHP?
• To understand a line of PHP

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. String Operators

• Difference between period and comma when concatenating with echo versus return?
• What does a . (dot) do in PHP?

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, Function Arguments

• Difference between period and comma when concatenating with echo versus return?

, Variable Declarations

• What do commas mean in a variable declaration?

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$$ Variable Variables

• What does $$ (dollar dollar or double dollar) mean in PHP?
• what is "$$" in PHP
• $function() and $$variable

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` Execution Operator

• What are the backticks `` called?

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<?= Short Open Tags

• What does this symbol mean in PHP <?=
• What does '<?=' mean in PHP?
• What does <?= mean?

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[] Arrays (short syntax since PHP 5.4)

• PHP arrays... What is/are the meaning(s) of an empty bracket?
• What is the meaning of []
• Php array_push() vs myArray[]
• What does [] mean when reading from a PHP array?
• Shorthand for arrays: literal $var = [] empty array

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<? Opening and Closing tags

• Are PHP short tags acceptable to use?

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... Argument unpacking (since PHP 5.6)

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** Exponentiation (since PHP 5.6)

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# One-line shell-style comment

• Can I use hashes for comments in PHP?

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转载于:https://stackoverflow.com/questions/3737139/reference-what-does-this-symbol-mean-in-php

Answer 1

Incrementing / Decrementing Operators

++ increment operator

-- decrement operator

Example    Name              Effect
---------------------------------------------------------------------
++$a       Pre-increment     Increments $a by one, then returns $a.
$a++       Post-increment    Returns $a, then increments $a by one.
--$a       Pre-decrement     Decrements $a by one, then returns $a.
$a--       Post-decrement    Returns $a, then decrements $a by one.

These can go before or after the variable.

If put before the variable, the increment/decrement operation is done to the variable first then the result is returned. If put after the variable, the variable is first returned, then the increment/decrement operation is done.

For example:

$apples = 10;
for ($i = 0; $i < 10; ++$i) {
    echo 'I have ' . $apples-- . " apples. I just ate one.\n";
}

Live example

In the case above ++$i is used, since it is faster. $i++ would have the same results.

Pre-increment is a little bit faster, because it really increments the variable and after that 'returns' the result. Post-increment creates a special variable, copies there the value of the first variable and only after the first variable is used, replaces its value with second's.

However, you must use $apples--, since first you want to display the current number of apples, and then you want to subtract one from it.

You can also increment letters in PHP:

$i = "a";
while ($i < "c") {
    echo $i++;
}

Once z is reached aa is next, and so on.

Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported.

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Stack Overflow Posts:

• Understanding Incrementing