Php variable in parentheses. PHP Operators

In the last post we looked at the syntax of the conditional statement in PHP. In this note we will talk about operator brackets. You will encounter them constantly. This is a basic concept of any programming language.

Wikipedia will help us answer the question of what operator brackets are:

Operator brackets- brackets or commands that define a block of commands in a programming language, perceived as a single whole, as one command.

IN Pascal language to denote operator brackets, the construction is used begin…. end. In C-like languages ​​(which includes PHP), operator brackets are described using symbols {…} .

Those. in other words, several commands enclosed in operator brackets are treated as 1 command.

There was an example in the article about conditions in PHP:

$b) ( echo "Variable A is greater than B"; ) else ( echo "Variable B is greater than A"; ) ?>

In this example, operator brackets are used 2 times. They frame the operators

• echo“Variable A is greater than B”;
• echo“Variable B is greater than A”;

In this example, there is only 1 statement enclosed in parentheses, so it is equivalent to writing something like this:

$b) echo "Variable A is greater than B"; else echo "Variable B is greater than A"; ?>

Syntax:

If (condition) expression 1; else expression 2;

Let's say we want to display another line on the screen if a condition is not met. Let's also change the values ​​of our variables so that now $a was > $b. Let's modify our code:

$b) echo "Variable A is greater than B."; else echo "Variable B is greater than A.";

echo "Yes..yes A is actually smaller than B."; ?>

Let's do it... What do we see on the screen:

Variable A is greater than B. Yes..yes A is actually less than B.

There's a mistake here somewhere. As you may have guessed, the whole point is that since our condition is true (a > b), the code is executed:

Echo "Variable A is greater than B."; In the thread else

We only have 1 expression:

Echo "Variable B is greater than A.";

$b) echo "Variable A is greater than B."; else echo "Variable B is greater than A."; echo "Yes..yes A is actually smaller than B."; ?>

Now we use operator brackets and combine 2 expressions in the branch In the thread:

$b) ( echo "Variable A is greater than B."; ) else ( echo "Variable B is greater than A."; echo "Yes..yes A is actually less than B."; ) ?>

The code has become much clearer. Now PHP understands that if the condition ($a > $b) is not met, it needs to print 2 lines. And if the condition is true - only one.

My big one for you advice– always use operator brackets, even if you do not need to combine several operators into 1 block. The fact is that:

• The code is easier to read this way. Taking a quick glance at the code, we see its individual blocks, and not a vinaigrette of letters and numbers.
• Changes often have to be made to old code. If you did not have operator brackets, and you (as in our case) added some code, then the program logic will be incorrect. You may not even notice it right away.

$GLOBALS variable. An associative array containing references to all script global scope variables defined in this moment. Variable names are array keys.

To declare a global variable, just place it in the $GLOBALS array

$GLOBALS["testkey2"]="testvalue2";

You can display all the values ​​of the $GLOBALS array variables using print_r($GLOBALS); or like this:

Foreach ($GLOBALS as $key=>$value) echo "GLOBALS[".$key."] == ".$value."
";

$_SERVER variable.

$_REQUEST variable- an associative array (array), which by default contains the data of the $_GET, $_POST and $_COOKIE variables. Variables in the $_REQUEST array are passed to the script using the GET, POST or COOKIE methods, so they cannot be trusted because they could have been changed by a remote user. Their presence and the order of adding data to the corresponding arrays is determined by the variables_order directive (GPCS is set by default).

$_SESSION variable

$_ENV variable. Filled in if the script was launched from command line. The $_SERVER array will contain all the variables from the $_ENV array.

$http_response_header variable

Simple syntax

If the interpreter encounters a dollar sign ($), it grabs as many characters as possible to form a valid variable name. If you want to specify the end of the name, enclose the variable name in braces.

$beer = "Heineken" ;
echo "$beer"s taste is great" ; // works, """ is an invalid character for a variable name
echo "He drank some $beers" ; // doesn't work, "s" is a valid character for a variable name
echo "He drank some $(beer)s" ; // works
echo "He drank some ($beer)s" ; // works
?>

An array element ( array) or object property ( object). In array indices there is a closing square bracket ( ] ) marks the end of the index definition. The same rules apply for object properties as for simple variables, although they cannot be tricked like they are with variables.

// These examples are specifically about using arrays internally
// lines. Outside of strings, always enclose the string keys of your
// array in quotes and do not use outside strings (brackets).

// Let's show all errors
error_reporting(E_ALL);

$fruits = array("strawberry" => "red" , "banana" => "yellow" );

// Works, but note that outside of the quoted string it works differently
echo "A banana is $fruits.";

//Works
echo "A banana is ($fruits["banana"]).";

// Works, but PHP, as described below, first looks for
// constant banana.
echo "A banana is ($fruits).";

// Doesn't work, use curly braces. This will cause a processing error.
echo "A banana is $fruits["banana"].";

// Works
echo "A banana is " . $fruits [ "banana" ] . "." ;

// Works
echo "This square is $square->width meters broad.";

// Does not work. See complex syntax for solution.
echo "This square is $square->width00 centimeters broad.";
?>

For more complex tasks you can use complex syntax.

Complex (curly) syntax

This syntax is called complex not because it is difficult to understand, but because it allows the use of complex expressions.

In fact, you can include any value that is in the namespace in a line with this syntax. You simply write the expression the same way you would outside the line, and then enclose it in ( and ). Since you cannot escape "(", this syntax will only be recognized when $ immediately follows (. (Use "(\$" or "\($" to escape "($"). Some illustrative examples:

// Let's show all errors
error_reporting(E_ALL);

$great = "fantastic" ;

// Doesn't work, will output: This is ( fantastic)
echo "This is ($great)" ;

// Works, prints: This is fantastic
echo "This is ($great)" ;
echo "This is $(great)" ;

// Works
echo "This square is ($square->width)00 centimeters wide.";

// Works
echo "It works: ($arr)";

// This is invalid for the same reason that $foo is invalid outside
// lines. In other words, it will still work,
// but since PHP looks for the constant foo first, this will cause
// level error E_NOTICE (undefined constant).
echo "This is wrong: ($arr)";

// Works. When using multidimensional arrays, inside
// lines always use curly braces
echo "This works: ($arr["foo"])";

// Works.
echo "This works: " . $arr [ "foo" ][ 3 ];

Echo "You can even write ($obj->values->name)";

Echo "This is the value of the variable named $name: ($($name))";
?>

Characters in strings can be used and modified by specifying their offset from the beginning of the string, starting at zero, in curly braces after the string. Here are some examples:

// Get the first character of the string
$str = "This is a test." ;
$first = $str ( 0 );

// Get the third character of the string
$third = $str ( 2 );

// Get the last character of the string
$str = "It's still a test.";
$last = $str ( strlen ($str ) - 1 );

// Change the last character of the line
$str = "Look at the sea";
$str ( strlen ($str ) - 1 ) = "self" ;

?>

String functions and operators

String operators

Different programming languages ​​use different string concatenation (joining) operators. For example, Pascal uses the "+" operator. Using the "+" operator to concatenate strings in PHP is incorrect: if the strings contain numbers, then instead of concatenating the strings, the operation of adding two numbers will be performed.

PHP has two operators that perform concatenation.

The first is the concatenation operator ("."), which returns the concatenation of the left and right arguments.

The second is an assignment operator with concatenation, which appends the right argument to the left one.

Let's give a specific example:

$a = "Hello" ;
$b = $a . "World!" ; // $b contains the string "Hello World!" - This is a concatenation

$a = "Hello" ;
$a .= "World!" ; // $a contains the string "Hello World!" - This is an assignment with concatenation
?>

String comparison operators

It is not recommended to use the comparison operators == and != to compare strings because they require type conversion. Example:

$x = 0 ;
$y=1;
if ($x == "" ) echo "

x- empty line

This script tells us that $x is an empty string. This is due to the fact that the empty string ("") is treated first as 0, and only then as "empty". In PHP, operands are compared as strings only if they are both strings. Otherwise they are compared as numbers. In this case, any string that PHP cannot convert to a number (including an empty string) will be treated as 0.

String comparison examples:

$x = "String" ;
$y = "String" ;
$ z = "Line" ;
if ($x == $z) echo "

String X equals string Z

To avoid confusion and type conversion, it is recommended to use the equivalence operator when comparing strings. The equivalence operator always allows you to compare strings correctly, since it compares values ​​both by value and by type:

$x = "String" ;
$y = "String" ;
$ z = "Line" ;
if ($x == = $z) echo "

String X equals string Z

Hello dear novice programmers. Let's continue to study the elements that make up.

In this article, we will learn what are php operators. In fact, we have been familiar with some of them almost since childhood, but we only know them as signs (+, -, =, !, ?).

In php, they are all called operators, which is quite logical, since they perform a specific action, or operation.

You could even say that all printable characters that are not a letter or a number are operators in PHP. But that’s not all, since there are operators consisting of letters.

Let's start in order.

Arithmetic operators

Arithmetic operators are used to perform operations on numbers.

+ is the addition operator;
— — subtraction operator;
/ - division operator;
* — multiplication operator;
% is the operator for obtaining the remainder during division;
++ — operator of increase by one (increment);
— — — decrease by one operator (decrement)

When writing, a space is usually placed before and after the operator. This is done solely for ease of reading the code, although this space does not affect anything, and you can do without it if you wish.

Complex expressions are composed according to the rules accepted in arithmetic, that is, multiplication and division have priority over addition and subtraction, and when both are present in the expression, the latter are enclosed in parentheses.

echo (6 + 7 ) * (7 + 8 );
?>

// 195 When performing an action, dividing an integer by an integer, in case of obtaining a remainder, the result is automatically converted to real number

(floating point number).
?>

echo 8 / 3 ;

//2.66666666666

The number of digits printed for a fractional number depends on the value set in the precision directive found in the php.ini file. Usually this is 12 characters not counting the period.
?>

The % operator is commonly used to determine whether one number is divisible by another without a remainder or not. echo 53328 % 4 ;//0 Actions with, since they involve two operands (term + term, dividend / divisor, etc.)

The actions of increment and decrement are called unary, since they involve one operand. Is there some more conditional operation, which involves three operands.

The increment (++) and decrement (- -) operators apply only to variables.

Variable type integer (whole numbers)

$next = 3 ;
echo +$next;
?>

// 4

Variable type string
$next = "abc";
?>

echo $next;

// abd

The letter "d" is printed instead of the letter "c" because it is next in the alphabet and we increased the value of the variable by one.

The examples show actions with increment, and in the same way you can perform actions with decrement. Bitwise operators Bitwise operators are designed to work with binary data. If anyone has no idea what it is, I’ll explain.

Binary numbers

are numbers like 1001000011100000111000.
Since such data is almost never used in website development, we will not dwell on it in detail. I’ll just show you what they look like, so that when you encounter such symbols you can imagine what you’re dealing with.
& - bitwise connection AND (and);
~ — bitwise negation (not);
<< — сдвиг влево битового значения операнда;
|

— bitwise union OR (or); ^ — bitwise elimination OR (xor);>> — shift to the right the bit value of the operand;

It is quite likely that you will encounter these operators, since binary data is widely used in the development of software programs.

computer graphics

. But to study them, if someone needs it, they will have to take a separate course on another resource.
Comparison Operators
< — оператор меньше;
<= — оператор меньше или равно;
Comparison operators are logical operators and are used to compare variables. Arrays and objects cannot be compared using them.
> - operator greater than;
=> - greater than or equal operator;
== — equality operator;

!= — inequality operator;

=== — equivalence operator (the value and type of the variable are equal);
!== — non-equivalence operator;< 0 ; // пустая строка
As a result of the comparison, either one is displayed on the screen, which corresponds to true, or an empty string, which corresponds to false.
echo 1 > 0 ;
?>

// 1

echo 1

echo 1 => 0 ;

The if statement takes a boolean variable, or expression, as an argument. If the condition is true, the result is displayed, if not true, an empty line is displayed.

if ($next< $nexT)
{
echo "Chance of precipitation"; // Output Precipitation possible
}
?>

$next = "Air humidity 80%";
$nexT = "Air humidity 90%";
if ($next > $nexT)
{
echo "Chance of precipitation"; // Print an empty line
}
?>

If the program needs to specify two actions, one of which will be performed if the value is true, and the other if the value is false, then together with the if statement, the else statement is used

$next = "Air humidity 80%";
$nexT = "Air humidity 90%";
if ($next > $nexT)
{
echo "Chance of precipitation";
}
In the thread
{
echo "No precipitation expected";
}
?>

In this case, “Precipitation is not expected” will be displayed, and if in the expression you change the sign “More” to “Less”, then “Precipitation is possible” will be displayed. This is how conditional operators check a condition and output the correct result according to it.

Very often there is a need to set more than two conditions, and then, to check them sequentially, the elseif operator is used.

if ($next > $nexT)
{
echo "I see";
}
elseif ($next<= $nexT)
{
echo "Snow";
}
elseif ($next >= $nexT)
{
echo "Rain";
}
elseif ($next == $nexT)
{
echo "Drought";
}
In the thread
{
echo "Chance of precipitation";
}
?>

This program will output "Snow". If none of the conditions matched, it would display “Chance of Precipitation.”

An if statement can contain as many elseif blocks as you like, but only one else statement.

An alternative recording option is allowed - without curly braces. In this case, the lines of the if, else, elseif statements end with a colon, and the entire construction is keyword(by the operator) endif .

$next = "Air humidity 50%";
$nexT = "Air humidity 60%";
if ($next<= $nexT):

echo "Snow";

elseif ($next >= $nexT):

echo "Rain";

elseif ($next == $nexT):

echo "Drought";

else:

echo "Chance of precipitation";
endif ;
?>

Logical operators

Logical operators are similar to bitwise operators. The difference between them is that the former operate with logical variables, and the latter with numbers.

Logical operators are used in cases where you need to combine several conditions, which will reduce the number of if statements, which in turn reduces the likelihood of errors in the code.

&& - connecting conjunction AND;
and - also AND, but with lower priority;
||
- separating conjunction OR;
or - also OR, but with lower priority;
xor - exclusive OR;

!

- denial;

Lower priority means that if both operators are present, the one with higher priority is executed first.

In the future, using examples of more complex scripts, we will dwell on logical operators in more detail.

Assignment operator
echo "Hello" // Hello
?>

Operator dot

The dot operator separates the integer part of a number from the fractional part, and combines several strings and a number into one whole string.

$next = 22 ;
echo "Today after" .$next. "frost is expected"; // Today after 22 frost is expected
?>

Parentheses operator

As in mathematics, the parentheses operator gives priority to the action enclosed within them.

The data enclosed in parentheses is executed first, and then all the rest.

Curly braces operator

There are three ways, or even styles, of placing curly braces in PHP.

1. BSD style - brackets are aligned to the left.

if ($next)
{

}

2. GNU style - brackets are aligned indented from the left edge

if ($next)
{
echo “Hello dear beginning programmers”;
}

3. K&R style - parenthesis opens on the operator line

if ($next)(
echo “Hello dear beginning programmers”;
}

From the very beginning, you need to choose one of the styles and in the future, when writing scripts, use only it. Moreover, it doesn’t matter at all which style you prefer. It is important that it be uniform throughout the program.

I think that's enough for now. In principle, not only signs, but also functions and other elements can be operators, so it is very difficult to list them all, and there is no point.

It is enough to have an idea of ​​the basic basics. And we will analyze the rest using practical examples.

An Irishman wanders around Sheremetyevo Airport in tears. One of the employees decided to sympathize:
— Do you miss your homeland?
- Not at all. I just lost all my luggage
- How could this happen?
- I don’t understand myself. Looks like I plugged the plug properly

For string interpolation. From the manual:

Complex (curly) syntax

It is not called complex because the syntax is complex and therefore allows for complex expressions.

Any scalar variable, array element, or object property with a string representation can be included through this syntax. Just write the expression as you would outside the string, and then wrap it in ( and ) . Since ( cannot be escaped, this syntax will only be recognized when $ follows ( . use (\$ to get the literal ($ . Some examples to make it clear:

width)00 centimeters broad."; // Works, quoted keys only work using the curly brace syntax echo "This works: ($arr["key"])"; // Works echo "This works: ($arr)" ; // This is wrong for the same reason as $foo is wrong outside a string. // In other words, it will still work, but only because PHP first looks for a // constant named foo; undefined constant) will be // thrown. echo "This is wrong: ($arr)"; arr["foo"])"; // Works. echo "This works: " . $arr["foo"]; echo "This works too: ($obj->values->name)"; echo "This is the value of the var named $name: ($($name))"; echo "This is the value of the var named by the return value of getName(): ($(getName()))"; echo "This is the value of the var named by the return value of \$object->getName(): ($($object->getName()))"; // Won"t work, outputs: This is the return value of getName(): (getName()) echo "This is the return value of getName(): (getName())"; ?>

Often this syntax is not needed. For example this:

$a = "abcd"; $out = "$a $a"; // "abcd abcd";

behaves exactly like this:

$out = "($a) ($a)"; // same

Thus, curly braces are not needed. But this:

$out = "$aefgh";

will, depending on your error level, either not work or create an error because there is no variable named $aefgh , so you need to do:

$out = "$(a)efgh"; // or $out = "($a)efgh";