Course Name - PHP
Data Types and Operators
PHP Data Types
Variables can store data of different types, and different data types can do different things.
PHP supports the following data types:
- String
- Integer
- Float (floating point numbers - also called double)
- Boolean
- Array
- Object
- NULL
- Resource
PHP String
A string is a sequence of characters, like "Hello world!".
A string can be any text inside quotes. You can use single or double quotes:
Example
<?php
$x = "Hello world!";
$y = 'Hello world!';
echo $x;
echo "<br>";
echo $y;
?>
//Output:Hello world!
Hello world!
PHP Integer
An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.
Rules for integers:
- An integer must have at least one digit
- An integer must not have a decimal point
- An integer can be either positive or negative
- Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0)
In the following example $x is an integer. The PHP var_dump() function returns the data type and value:
Example
<?php
$x = 5985;
var_dump($x);
?>
//Output: int(5985)
PHP Float
A float (floating point number) is a number with a decimal point or a number in exponential form.
In the following example $x is a float. The PHP var_dump() function returns the data type and value:
Example
<?php
$x = 10.365;
var_dump($x);
?>
//Output: float(10.365)
PHP Boolean
A Boolean represents two possible states: TRUE or FALSE.
$x = true;
$y = false;
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.
PHP Array
An array stores multiple values in one single variable.
In the following example $cars is an array. The PHP var_dump() function returns the data type and value:
Example
<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>
//Output: array(3) { [0]=> string(5) "Volvo" [1]=> string(3) "BMW" [2]=> string(6) "Toyota" }
PHP Object
An object is a data type which stores data and information on how to process that data.
In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods:
Example
<?php
class Car {
function Car() {
$this->model = "VW";
}
}
// create an object
$herbie = new Car();
// show object properties
echo $herbie->model;
?>
//Output: VW
PHP NULL Value
Null is a special data type which can have only one value: NULL.
A variable of data type NULL is a variable that has no value assigned to it.
Tip: If a variable is created without a value, it is automatically assigned a value of NULL.
Variables can also be emptied by setting the value to NULL:
Example
<?php
$x = "Hello world!";
$x = null;
var_dump($x);
?>
//Output:NULL
PHP Resource
The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP.
A common example of using the resource data type is a database call.
Strings
A string is a sequence of characters, like "Hello world!".
The PHP strlen() function returns the length of a string.
The example below returns the length of the string "Hello world!":
Example
<?php
echo strlen("Hello world!"); // Output: 12
?>
The output of the code above will be: 12.
Count The Number of Words in a String
The PHP str_word_count() function counts the number of words in a string:
Example
<?php
echo str_word_count("Hello world!"); // Output: 2
?>
The output of the code above will be: 2.
Reverse a String
The PHP strrev() function reverses a string:
Example
<?php
echo strrev("Hello world!"); // Output: !dlrow olleH
?>
The output of the code above will be: !dlrow olleH.
Search For a Specific Text Within a String
The PHP strpos() function searches for a specific text within a string.
If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE.
The example below searches for the text "world" in the string "Hello world!":
Example
<?php
echo strpos("Hello world!", "world"); // Output: 6
?>
The output of the code above will be: 6.
Tip: The first character position in a string is 0 (not 1).
Replace Text Within a String
The PHP str_replace() function replaces some characters with some other characters in a string.
The example below replaces the text "world" with "Dolly":
Example
<?php
echo str_replace("world", "Dolly", "Hello world!"); // Output: Hello Dolly!
?>
The output of the code above will be: Hello Dolly!
PHP Constants
Constants are like variables except that once they are defined they cannot be changed or undefined.
A constant is an identifier (name) for a simple value. The value cannot be changed during the script.
A valid constant name starts with a letter or underscore (no $ sign before the constant name).
Note: Unlike variables, constants are automatically global across the entire script.
Create a PHP Constant
To create a constant, use the define() function.
Syntax
define(name, value, case-insensitive)
Parameters:
- name: Specifies the name of the constant
- value: Specifies the value of the constant
- case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false
The example below creates a constant with a case-sensitive name:
Example
<?php
define("GREETING", "Welcome to W3Schools.com!");
echo GREETING;
?>
//Output:Welcome to W3Schools.com!
The example below creates a constant with a case-insensitive name:
Example
<?php
define("GREETING", "Welcome to W3Schools.com!", true);
echo greeting;
?>
//Output:Welcome to W3Schools.com!
Constants are Global
Constants are automatically global and can be used across the entire script.
The example below uses a constant inside a function, even if it is defined outside the function:
Example
<?php
define("GREETING", "Welcome to W3Schools.com!");
function myTest() {
echo GREETING;
}
myTest();
?>
//Output:Welcome to W3Schools.com!
PHP Operators
Operators are used to perform operations on variables and values.
PHP divides the operators in the following groups:
- Arithmetic operators
- Assignment operators
- Comparison operators
- Increment/Decrement operators
- Logical operators
- String operators
- Array operators
PHP Arithmetic Operators
The PHP arithmetic operators are used with numeric values to perform common arithmetical operations, such as addition, subtraction, multiplication etc.
| Operator | Name | Example | Result | |
|---|---|---|---|---|
| + | Addition | $x + $y | Sum of $x and $y | |
| - | Subtraction | $x - $y | Difference of $x and $y | |
| * | Multiplication | $x * $y | Product of $x and $y | |
| / | Division | $x / $y | Quotient of $x and $y | |
| % | Modulus | $x % $y | Remainder of $x divided by $y | |
| ** | Exponentiation | $x ** $y | Result of raising $x to the $y'th power (Introduced in PHP 5.6) |
PHP Assignment Operators
The PHP assignment operators are used with numeric values to write a value to a variable.
The basic assignment operator in PHP is "=". It means that the left operand gets set to the value of the assignment expression on the right.
| Assignment | Same as... | Description |
|---|---|---|
| x = y | x = y | The left operand gets set to the value of the expression on the right |
| x += y | x = x + y | Addition |
| x -= y | x = x - y | Subtraction |
| x *= y | x = x * y | Multiplication |
| x /= y | x = x / y | Division |
| x %= y | x = x % y | Modulus |
PHP Comparison Operators
The PHP comparison operators are used to compare two values (number or string):
| Operator | Name | Example | Result |
|---|---|---|---|
| == | Equal | $x == $y | Returns true if $x is equal to $y |
| === | Identical | $x === $y | Returns true if $x is equal to $y, and they are of the same type |
| != | Not equal | $x != $y | Returns true if $x is not equal to $y |
| <> | Not equal | $x <> $y | Returns true if $x is not equal to $y |
| !== | Not identical | $x !== $y | Returns true if $x is not equal to $y, or they are not of the same type |
| > | Greater than | $x > $y | Returns true if $x is greater than $y |
| < | Less than | $x < $y | Returns true if $x is less than $y |
| >= | Greater than or equal to | $x >= $y | Returns true if $x is greater than or equal to $y |
| <= | Less than or equal to | $x <= $y | Returns true if $x is less than or equal to $y |
PHP Increment / Decrement Operators
The PHP increment operators are used to increment a variable's value.
The PHP decrement operators are used to decrement a variable's value.
| Operator | Name | Description |
|---|---|---|
| ++$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 |
PHP Logical Operators
The PHP logical operators are used to combine conditional statements.
| Operator | Name | Example | Result |
|---|---|---|---|
| and | And | $x and $y | True if both $x and $y are true |
| or | Or | $x or $y | True if either $x or $y is true |
| xor | Xor | $x xor $y | True if either $x or $y is true, but not both |
| && | And | $x && $y | True if both $x and $y are true |
| || | Or | $x || $y | True if either $x or $y is true |
| ! | Not | !$x | True if $x is not true |
PHP String Operators
PHP has two operators that are specially designed for strings.
| Operator | Name | Example | Result |
|---|---|---|---|
| . | Concatenation | $txt1 . $txt2 | Concatenation of $txt1 and $txt2 |
| .= | Concatenation assignment | $txt1 .= $txt2 | Appends $txt2 to $txt1 |
PHP Array Operators
The PHP array operators are used to compare arrays.
| Operator | Name | Example | Result |
|---|---|---|---|
| + | Union | $x + $y | Union of $x and $y |
| == | Equality | $x == $y | Returns true if $x and $y have the same key/value pairs |
| === | Identity | $x === $y | Returns true if $x and $y have the same key/value pairs in the same order and of the same types |
| != | Inequality | $x != $y | Returns true if $x is not equal to $y |
| <> | Inequality | $x <> $y | Returns true if $x is not equal to $y |
| !== | Non-identity | $x !== $y | Returns true if $x is not identical to $y |
Precedence of PHP Operators
Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator −
For example x = 7 + 3 * 2; Here x is assigned 13, not 20 because operator * has higher precedence than + so it first get multiplied with 3*2 and then adds into 7.
Here operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.
| Category | Operator | Associativity |
|---|---|---|
| Unary | ! ++ -- | Right to left |
| Multiplicative | * / % | Left to right |
| Additive | + - | Left to right |
| Relational | < <= > >= | Left to right |
| Equality | == != | Left to right |
| Logical AND | && | Left to right |
| Logical OR | || | Left to right |
| Conditional | ?: | Right to left |
| Assignment | = += -= *= /= %= | Right to left |
