Expressions in PHP are fundamental elements used to perform various operations on variables and values. They are used to evaluate values, compare values, and control program flow. Understanding expressions is critical to writing efficient and effective PHP code.

Table of Contents

## Arithmetic expressions

Arithmetic expressions involve mathematical operations such as addition, subtraction, multiplication, and division. The most common arithmetic operators in PHP are +, -, *, and /. An example of an arithmetic expression is:

```
$x = 10;
$y = 5;
$sum = $x + $y;
echo $sum; // output: 15
```

## Comparison Expressions

Comparison expressions are used to compare values using operators such as ==, !=, >, <, >=, and <=. The result of a comparison expression is a boolean value – true or false. An example of a comparison expression is:

```
$x = 10;
$y = 5;
if ($x > $y) {
echo "x is greater than y";
} else {
echo "y is greater than x";
}
```

## Logical Expressions

Logical expressions are used to evaluate the truth value of two or more expressions using logical operators such as && (and), || (or), and ! (not). An example of a logical expression is:

```
$x = 10;
$y = 5;
if ($x > 5 && $y < 10) {
echo "both conditions are true";
}
```

## String Expressions

String expressions are used to manipulate and concatenate strings using the “.” operator. An example of a string expression is:

```
$greeting = "Hello";
$name = "John";
$message = $greeting . " " . $name;
echo $message; // output: Hello John
```

## Conditional expressions

Conditional expressions are used to control program flow using the ternary operator (?:) and the null coalescing operator (??). An example of a conditional expression is:

```
$username = isset($_POST['username']) ? $_POST['username'] : 'Guest';
echo $username; // output: Guest if $_POST['username'] is not set
```

Learn how to use PHP operators with PHP expressions.

## Conclusion

Understanding expressions in PHP is crucial to writing efficient and effective code. By mastering arithmetic, comparison, logical, string, and conditional expressions, you’ll be able to manipulate values, control program flow, and create complex logic in your PHP applications.