Logical Operators in PHP: A Comprehensive Guide

In CSS (Cascading Style Sheets), logical operators are not directly used for defining styles. CSS is primarily a styling language that is used to describe the presentation of a document written in HTML (Hypertext Markup Language). Logical operators, on the other hand, are used in programming languages to combine or evaluate logical conditions.

While these selectors can be combined to create more complex conditions, CSS does not provide logical operators like AND (&&) or OR (||) that are commonly used in programming languages. If you need to apply different styles based on multiple conditions, you might need to use JavaScript or preprocessors like Sass or Less that support logical operators and allow you to generate CSS styles dynamically.

AND operator

In PHP, the logical AND operator (&&) is used to combine two or more conditions and evaluate whether all of them are true. It returns true if all the conditions are true, and false otherwise. The AND operator is often used in conditional statements and logical expressions to make decisions based on multiple conditions.

Here's the syntax for the AND operator in PHP:

  $result = $condition1 && $condition2;

In the above code, $condition1 and $condition2 are boolean expressions or variables that represent conditions. The result of the AND operator is stored in the $result variable.

The behaviour of the AND operator can be summarized as follows:

AND operator For example:

If both $condition1 and $condition2 are true, the result will be true.
If either $condition1 or $condition2 (or both) is false, the result will be false.

Here's an example to illustrate the usage of the AND operator:

<?php
   $eng=98;
   $mat=85;
   $sci=85;
   var_dump($eng>=35 and $mat>=35 and $sci>=35);
?>

The provided code is written in PHP and performs a logical operation using the and operator (&&). Let's go through the code step by step

First we declare three variables are declared and assigned values. $eng is assigned a value of 98, $mat is assigned a value of 85, and $sci is also assigned a value of 85. These variables likely represent scores or grades in different subjects.
var_dump() function to output the result of the logical expression. The expression being evaluated is $eng >= 35 and $mat >= 35 and $sci >= 35. It checks if all three variables ($eng, $mat, and $sci) have values greater than or equal to 35.

The var_dump() function is used to display the result of the logical expression. It provides detailed information about the result, including the data type (bool) and the value (true or false).

<?php
   $eng=98;
   $mat=85;
   $sci=85;
   var_dump($eng>=35 && $mat>=35 && $sci>=35);
?>

Both the and and && operators serve the same purpose of performing logical conjunction, but their precedence difference can affect how expressions are evaluated in complex conditions.

The && operator (logical AND operator) is used to combine the conditions. It returns true if all conditions are true; otherwise, it returns false . In this case, the expression will return true if all three subjects have scores greater than or equal to 35.

The var_dump() function is used to display the result of the logical expression. It provides detailed information about the result, including the data type ( bool ) and the value ( true or false ).

Overall, the code is checking if the scores in English, Math, and Science are all greater than or equal to 35. If all three conditions are met, it will output bool(true) using var_dump() . Otherwise, it will output bool(false) . The && operator is used for short-circuit evaluation, which means if the first condition is false, it won't evaluate the remaining conditions since the result will be false regardless.

OR operator

In PHP, the or operator (also known as the logical OR operator) is used for logical disjunction. It evaluates two expressions and returns true if at least one of the expressions evaluates to true, otherwise it returns false.

In PHP, the or operator (also known as the logical OR operator) is used for logical disjunction. It evaluates two expressions and returns true if at least one of the expressions evaluates to true, otherwise it returns false.

Here's an example to demonstrate the usage of the or operator:

<?php
   $eng=98;
   $mat=85;
   $sci=85;
   var_dump($eng>=35 or $mat>=35 or $sci>=35);
?>

The expression being evaluated is $eng >= 35 or $mat >= 35 or $sci >= 35. It checks if at least one of the variables ($eng, $mat, or $sci) has a value greater than or equal to 35.

Similarly, you can use the || operator, which is an alternative syntax for the or operator. Both or and || perform the same logical disjunction operation.

It's important to note that the or operator has a lower precedence than the || operator. This means that when both or and || operators are used in an expression, the || operator will be evaluated first.

Here's an example to illustrate the precedence difference:

<?php
   $eng=98;
   $mat=85;
   $sci=85;
   var_dump($eng>=35 || $mat>=35 || $sci>=35);
?>

var_dump() function to output the result of the logical expression. The expression being evaluated is $eng >= 35 || $mat >= 35 || $sci >= 35. It checks if at least one of the variables ($eng, $mat, or $sci) has a value greater than or equal to 35.

Both the or and || operators serve the same purpose of performing logical disjunction, but their precedence difference can affect how expressions are evaluated in complex conditions.

NOT operator

In PHP, the ! operator (exclamation mark) is used as the logical NOT operator. It is a unary operator that negates the value of an expression. It returns true if the expression is false, and false if the expression is true .

Here's an example to demonstrate the usage of the ! operator:

<?php
   $eng=98;
   var_dump(!$eng>=35);
?>

var_dump() function to output the result of the logical expression. The expression being evaluated is !$eng >= 35.
The ! operator negates the value of $eng. Since $eng has a value of 98, which is considered truthy, the !$eng expression evaluates to false.
The >= operator is used to compare the result of !$eng (which is false) with the value 35. However, it's important to note that the !$eng expression is evaluated first due to the operator precedence rules.
So effectively, the expression !$eng >= 35 is equivalent to false >= 35. In this case, the comparison operator >= is comparing false with 35, which performs a type conversion. In PHP, false is considered less than any non-zero value, so the expression false >= 35 evaluates to false.

The logical NOT operator is useful for negating conditions or flipping boolean values, allowing you to perform logical operations based on the opposite of a given condition.

XOR operator

In PHP, the xor operator is used as the logical XOR (exclusive OR) operator. It compares two expressions and returns true if exactly one of the expressions is true, and false otherwise.

Here's an example to demonstrate the usage of the xor operator:

<?php
   $a=true;
   $b=false;
   var_dump($a xor $b);
?>

The xor operator ensures that only one condition is true for the overall expression to be considered true. If both conditions are true or both conditions are false, the xor operator returns false.

var_dump() function to output the result of the logical expression $a xor $b.

The xor operator compares the values of $a and $b and returns true if exactly one of the variables is true. Otherwise, if both variables are either true or false, thexor operator returns false.

In this case, the value of $a is true and the value of $b is false. Since exactly one of the variables is true, the expression $a xor $b evaluates to true.

It's important to note that the xor operator does not perform short-circuit evaluation. This means that both expressions are always evaluated, regardless of the value of the first expression. Therefore, be cautious when using the xor operator with expressions that may have side effects.

Overall, the xor operator in PHP allows you to perform exclusive OR operations, where only one of the expressions needs to be true for the result to be true.