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

    File: variable1.php

                   
            
                     
<?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

    
<?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 "color" is different from Color, COLOR, COLor etc.

    File: variable3.php 

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

    Output

    My car is red Notice: Undefined variable: COLOR in C:wampwwwvariable.php on line 4 My house is Notice: Undefined variable: coLOR in C:wampwwwvariable.php on line 5 My boat is

    PHP Variable: Rules


  • PHP variables must start with letter or underscore only.

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

    • File: variablevalid.php

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

    Output

    hello hello

    File: variableinvalid.php

            
<?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:wampwwwvariableinvalid.php on line 2

    PHP: Loosely typed language

    PHP is a loosely typed language, it means PHP automatically converts the variable to its correct data type.