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Variables are used for storing values, such as numbers, strings or function results, so that they can be used many times in a script.


Variables in PHP

Variables are used for storing a values, like text strings, numbers or arrays.

When a variable is set it can be used over and over again in your script

All variables in PHP start with a $ sign symbol.

The correct way of setting a variable in PHP:

$var_name = value;

New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.

Let’s try creating a variable with a string, and a variable with a number:

<?php
$txt = "Hello World!";
$number = 16;
?>

PHP is a Loosely Typed Language

In PHP a variable does not need to be declared before being set.

In the example above, you see that you do not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on how they are set.

In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

In PHP the variable is declared automatically when you use it.


Variable Naming Rules

  • A variable name must start with a letter or an underscore “_”
  • A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ )
  • A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)

A string variable is used to store and manipulate a piece of text.


Strings in PHP

String variables are used for values that contains character strings.

In this tutorial we are going to look at some of the most common functions and operators used to manipulate strings in PHP.

After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the string “Hello World” to a string variable called $txt:

<?php
$txt="Hello World";
echo $txt;
?>

The output of the code above will be:

Hello World

Now, lets try to use some different functions and operators to manipulate our string.


The Concatenation Operator

There is only one string operator in PHP.

The concatenation operator (.)  is used to put two string values together.

To concatenate two variables together, use the dot (.) operator:

<?php
$txt1="Hello World";
$txt2="1234";
echo $txt1 . " " . $txt2;
?>

The output of the code above will be:

Hello World 1234

If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string.

Between the two string variables we added a string with a single character, an empty space, to separate the two variables.


Using the strlen() function

The strlen() function is used to find the length of a string.

Let’s find the length of our string “Hello world!”:

<?php
echo strlen("Hello world!");
?>

The output of the code above will be:

12

The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string)


Using the strpos() function

The strpos() function is used to search for a string or character within a string.

If a match is found in the string, this function will return the position of the first match. If no match is found, it will return FALSE.

Let’s see if we can find the string “world” in our string:

Operators are used to operate on values.


PHP Operators

This section lists the different operators used in PHP.

Arithmetic Operators

Operator Description Example Result
+ Addition x=2
x+2
4
Subtraction x=2
5-x
3
* Multiplication x=4
x*5
20
/ Division 15/5
5/2
3
2.5
% Modulus (division remainder) 5%2
10%8
10%2
1
2
0
++ Increment x=5
x++
x=6
Decrement x=5
x–
x=4

Assignment Operators

Operator Example Is The Same As
= x=y x=y
+= x+=y x=x+y
-= x-=y x=x-y
*= x*=y x=x*y
/= x/=y x=x/y
.= x.=y x=x.y
%= x%=y x=x%y

Comparison Operators

Operator Description Example
== is equal to 5==8 returns false
!= is not equal 5!=8 returns true
> is greater than 5>8 returns false
< is less than 5<8 returns true
>= is greater than or equal to 5>=8 returns false
<= is less than or equal to 5<=8 returns true

Logical Operators

Operator Description Example
&& and x=6
y=3(x < 10 && y > 1) returns true
|| or x=6
y=3(x==5 || y==5) returns false
! not x=6
y=3!(x==y) returns tru

The output of the code above will be:

6

As you see the position of the string “world” in our string is position 6. The reason that it is 6, and not 7, is that the first position in the string is 0, and not 1.


Complete PHP String Reference

For a complete reference of all string functions, go to our complete PHP String Reference.

The reference contains a brief description and examples of use for each function

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