PHP Operators
PHP Operators
PHP operators are symbols or keywords used to perform various operations on values or variables. Here are some of the most commonly used PHP operators:
- Arithmetic operators:
- Addition: +
- Subtraction: –
- Multiplication: *
- Division: /
- Modulus: % (returns the remainder of a division operation)
- Exponentiation: ** (raises a number to a power)
- Assignment operators:
- Assignment: =
- Addition assignment: +=
- Subtraction assignment: -=
- Multiplication assignment: *=
- Division assignment: /=
- Modulus assignment: %=
- Concatenation assignment: .= (joins two strings together)
- Comparison operators:
- Equal to: ==
- Identical to: === (compares value and type)
- Not equal to: !=
- Not identical to: !==
- Greater than: >
- Less than: <
- Greater than or equal to: >=
- Less than or equal to: <=
- Logical operators:
- And: &&
- Or: ||
- Not: !
- Increment and decrement operators:
- Increment: ++
- Decrement: —
- Ternary operator:
- ?: (used for conditional expressions)
- Bitwise operators:
- And: &
- Or: |
- Xor: ^
- Not: ~
- Left shift: <<
- Right shift: >>
These are just a few of the many operators available in PHP.
Execution Operators in php:
In PHP, execution operators are used to execute external commands or programs and capture their output. The two execution operators are:
- Backtick operator: “ The backtick operator is used to execute a command and return its output as a string. For example, if you want to execute the ls command to list the files in the current directory, you can use the backtick operator like this:
$output = `ls`;
echo $output;
This will execute the ls command and store its output in the $output variable, which is then printed to the screen.
- Shell_exec function: The shell_exec() function is used to execute a command and return its output as a string. For example, to execute the ls command, you can use the shell_exec() function like this:
$output = shell_exec('ls');
echo $output;
This will execute the ls command and store its output in the $output variable, which is then printed to the screen.
Note that the backtick operator and shell_exec() function can be used to execute any command or program, not just shell commands. However, be careful when using these operators, as they can be a security risk if you are executing user-supplied input without proper validation.
Error Control Operators:
In PHP, error control operators are used to suppress error messages or warnings that would normally be displayed when a script runs into an error. There are two error control operators in PHP:
- The at sign (@): The at sign (@) is used to suppress errors and warnings that are generated by a line of code. For example, if you want to suppress a warning message that may be generated by the file_get_contents() function if the file doesn’t exist, you can use the at sign like this:
$content = @file_get_contents('non_existent_file.txt');
In this example, the at sign suppresses any warning messages that may be generated by the file_get_contents() function if the file doesn’t exist.
However, it is generally not recommended to use the at sign to suppress errors, as it can make debugging more difficult and hide potentially important error messages.
- The error suppression operator (): The error suppression operator () can also be used to suppress errors and warnings that are generated by a line of code. For example:
$content = file_get_contents('non_existent_file.txt');
In this example, the error suppression operator is used to suppress any warning messages that may be generated by the file_get_contents() function if the file doesn’t exist. However, like the at sign, it is generally not recommended to use the error suppression operator to suppress errors.
It is important to note that while error control operators can be useful in certain situations, they should be used with caution. It is always best to properly handle errors and warnings in your code to ensure that your script runs smoothly and any potential issues are addressed appropriately.
PHP Operators Precedence:
In PHP, operators precedence is the order in which operators are evaluated in an expression. The order of precedence determines which operations are performed first in an expression when more than one operator is used.
Here is a list of PHP operators, listed in order of precedence (highest to lowest):
- Parentheses: ( )
- Increment/Decrement: ++, —
- Logical NOT: !
- Multiplication, Division, Modulus: *, /, %
- Addition, Subtraction: +, –
- String Concatenation: .
- Comparison: <, >, <=, >=, ==, !=, ===, !==
- Logical AND: &&
- Logical OR: ||
- Ternary: ? :
- Assignment: =, +=, -=, *=, /=, %=, .=
It is important to note that the order of evaluation can be changed by using parentheses to group parts of an expression, forcing the evaluation of certain operations before others.
For example, the expression $result = 10 + 5 * 2 would evaluate to 20, because the multiplication operation is performed before the addition operation. However, if we use parentheses to group the addition operation first, like this: $result = (10 + 5) * 2, the expression would evaluate to 30, because the addition operation is performed before the multiplication operation.
Understanding operator precedence is important in writing correct and efficient code in PHP.