Reference - What does this symbol mean in PHP?
51
This is a collection of questions that come up every now and then about syntax in PHP. This is also a Community Wiki, so everyone is invited to participate in maintaining this list. 

It used to be hard to find questions about operators and other syntax tokens.¹
The main idea is to have links to existing questions on Stack Overflow, so it's easier for us to reference them, not to copy over content from the PHP Manual.

¹ Note: Since January 2013, Stack Overflow does support special characters. Just surround the search terms by quotes, e.g. [php] "==" vs "==="

If you have been pointed here by someone because you have asked such a question, please find the particular syntax below. The linked pages to the PHP manual along with the linked questions will likely answer your question then. If so, you are encouraged to upvote the answer. This list is not meant as a substitute to the help others provided.

If your particular token is not listed below, you might find it in the List of Parser Tokens.

& Bitwise Operators or References

=& References

&= Bitwise Operators

&& Logical Operators

% Arithmetic Operators

!! Logical Operators

@ Error Control Operators

?: Ternary Operator

: Alternative syntax for control structures, Ternary Operator

:: Scope Resolution Operator

\ Namespaces

-> Classes And Objects

=> Arrays

^ Bitwise Operators

>> Bitwise Operators

<< Bitwise Operators

<<< Heredoc or Nowdoc

= Assignment Operators

== Comparison Operators

=== Comparison Operators

!== Comparison Operators

!= Comparison Operators

<> Comparison Operators

| Bitwise Operators

|| Logical Operators

~ Bitwise Operators

+ Arithmetic Operators, Array Operators

+= Assignment Operators

++ Incrementing/Decrementing Operators

.= Assignment Operators

. String Operators

, Function Arguments

$$ Variable Variables

` Execution Operator

<?= Short Open Tags

[] Arrays

<? Opening and Closing tags
improve this question | comment
Krystina Shields Created at: 2013-11-13 17:07:06 UTC By Krystina Shields
I know this isn't strictly PHP, but what about including a link to phpdoc.org for phpDocumentor comment syntax, which is commonly used and it's also impossible to search for /**? - Emanuel Heathcote
Can I suggest square bracket and curly bracket ? - Chandler Von
I ran into this problem a lot too (not being able to search for special characters), which is why I made SymbolHound, a search engine that doesn't ignore special characters. I also posted it on StackApps. - Daphnee Spencer
Well, from the heading Why is this?, I'd guess it's because "The main idea is to have links to existing questions on Stack Overflow, so it's easier for us to reference them". - Miss Berniece Prohaska
6 Answers
0
Type Operators ¶

instanceof is used to determine whether a PHP variable is an instantiated object of a certain class 

<?php class mclass { } class sclass { } $a = new mclass; var_dump($a instanceof mclass);var_dump($a instanceof sclass);?>


The above example will output: ¶

bool(true)
  bool(false)

Reason : Above Example $a is a object of the mclass so use onlu a mclass data not instance of with the sclass

2)Type Operators Example with inherited ¶

sfddfgd<?php class pclass { } class childclass extends pclass { } $a = new childclass; var_dump($a instanceof childclass); var_dump($a instanceof pclass);

The above example will output: ¶

bool(true)
bool(true)
0
    syntax    name              description 
    x == y    Equality          True if x and y have the same key/value pairs
    x != y    Inequality        True if x is not equal to y
    x === y   Identity          True if x and y have the same key/value pairs in 
                                  the same order and of the same types
    x !== y   Non-identity      True if x is not identical to y
    ++ x      Pre-increment     Increments x by one, then returns x
    x ++      Post-increment    Returns x, then increments x by one
    -- x      Pre-decrement     Decrements x by one, then returns x
    x --      Post-decrement    Returns x, then decrements x by one
    x and y   And               True if both x and y are true x=6 y=3 
                                  (x < 10 and y > 1) returns true
    x && y    And               True if both x and y are true x=6 y=3 
                                  (x < 10 && y > 1) returns true
    a . b     Concatenation     Concatenate two strings: "Hi" . "Ha" 

0
_ Alias for gettext()  

The underscore character '_' is an alias to gettext(). 
0
Bitwise Operator

What is a bit? A bit is a representation of 1 or 0. Basically OFF(0) and ON(1)

What is a byte? A byte is made up of 8 bits and the highest value of a byte is 255, which would mean every bit is set. We will look at why a byte's maximum value is 255.

-------------------------------------------
|      1 Byte ( 8 bits )                  |
-------------------------------------------
|Place Value | 128| 64| 32| 16| 8| 4| 2| 1|     
-------------------------------------------


This representation of 1 Byte

1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255 (1 Byte) 

A few examples for better understanding

The "AND" operator: &

$a =  9;
$b = 10;
echo $a & $b;


This would output the number 8. Why? Well let's see using our table example.

-------------------------------------------
|      1 Byte ( 8 bits )                  |
-------------------------------------------
|Place Value | 128| 64| 32| 16| 8| 4| 2| 1|     
-------------------------------------------
|      $a    |   0|  0|  0|  0| 1| 0| 0| 1|    
-------------------------------------------
|      $b    |   0|  0|  0|  0| 1| 0| 1| 0|
------------------------------------------- 


So you can see from the table the only bit they share together is the 8 bit.

Second example

$a =  36;
$b = 103;
echo $a & $b; // This would output the number 36.
$a = 00100100
$b = 01100111


The two shared bits are 32 and 4, which when added together return 36.

The "Or" operator: |

$a =  9;
$b = 10;
echo $a | $b;


This would output the number 11. Why?

$a = 00001001
$b = 00001010


You will notice that we have 3 bits set, in the 8, 2, and 1 columns. Add those up: 8+2+1=11.
0
Magic constants: Although these are not just symbols but important part of this token family. There are eight magical constants that change depending on where they are used. 

0
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. Putting this operator before the variable is slightly faster.

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.

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.


Stack Overflow Posts:

Understanding Incrementing  
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