PHP Tutorial Part 6 : PHP - Variables

PHP Variables

In PHP, a variable is declared using a $ sign followed by the variable name. Here, some important points to know about variables:

• As PHP is a loosely typed language, so we do not need to declare the data types of the variables. It automatically analyzes the values and makes conversions to its correct datatype.
• After declaring a variable, it can be reused throughout the code.
• Assignment Operator (=) is used to assign the value to a variable.

Syntax of declaring a variable in PHP is given below:

$variablename=value;  

Rules for declaring PHP variable:

• A variable must start with a dollar ($) sign, followed by the variable name.
• It can only contain alpha-numeric character and underscore (A-z, 0-9, _).
• A variable name must start with a letter or underscore (_) character.
• A PHP variable name cannot contain spaces.
• One thing to be kept in mind that the variable name cannot start with a number or special symbols.
• PHP variables are case-sensitive, so $name and $NAME both are treated as different variable.

PHP Variable: Declaring string, integer, and float 

Let's see the example to store string, integer, and float values in PHP variables.

File: variable1.php

Example-

<?php $str="hello string"; $x=200; $y=44.6; echo "string is: $str <br/>"; echo "integer is: $x <br/>"; echo "float is: $y <br/>"; ?>

Output: 

 string is: hello string

 integer is: 200

 float is: 44.6 `

PHP Variable: Sum of two variables

File: variable2.php

Example-

<?php $x=5; $y=6; $z=$x+$y; echo $z; ?>

Output: 

11

PHP Variable: case sensitive

In PHP, variable names are case sensitive. So variable name "colour" is different from Color, COLOR, COLor etc.

File: variable3.php

Example-

<?php $color="red"; echo "My car is " . $color . "<br>"; echo "My house is " . $COLOR . "<br>"; echo "My boat is " . $coLOR . "<br>"; ?>

Output:

My car is red

Notice: Undefined variable: COLOR in C:\wamp\www\variable.php on line 4

My house is 

Notice: Undefined variable: coLOR in C:\wamp\www\variable.php on line 5

My boat is 

PHP Variable: Rules

PHP variables must start with a letter or underscore only.

PHP variable can't start with numbers and special symbols.

File: variablevalid.php

Example-

<?php $a="hello";//letter (valid) $_b="hello";//underscore (valid) echo "$a <br/> $_b"; ?>

Output:

hello 

hello

File: variableinvalid.php

Example-

<?php $4c="hello";//number (invalid) $*d="hello";//special symbol (invalid) echo "$4c <br/> $*d"; ?>

Output:

Parse error: syntax error, unexpected '4' (T_LNUMBER), expecting variable (T_VARIABLE)

 or '$' in C:\wamp\www\variableinvalid.php on line 2