Variables in PHP

Variables in PHP is basically a single or a combination of characters, followed by a $ sign, used to store information. Therefore we can also say that, variables are the containers, used to store information. For example:

<?php
   $x = "codescracker.com";
   echo "$x";
?>

The output of above PHP example is shown in the snapshot given below:

Note - The echo statement/keyword is used to output data.

In above example, the variable $x stores codescracker.com. Therefore using the statement:

echo "$x";

The value of $x was printed on the output.

Rules to Name a Variable in PHP

The first and most important rule to create/name a variable in PHP is, every variable must start with a $ character.

The second rule is, every variable must start with either alphabet characters (A-Z, a-z) or an underscore character (_).

The third rule is, every variable must be named using either alpha-numeric characters (A-Z, a-z, 0-9) or an underscore character (_).

The fourth rule is, do not forget that variables in PHP are case-sensitive. It means that $x and $X are two different variables. Similarly $city, $City, and $CITY are all three different variables.

Here are the list of some valid variable names in PHP:

• $x
• $y
• $city
• $mycity
• $my_city
• $MyCity
• $myCity
• $_city
• $_city_
• $address
• $address23
• $address23albert

Let me create an example, that uses all the above valid PHP variables:

<?php
   $x = 1;
   $y = 2;
   $city = "Vancouver";
   $mycity = "Munich";
   $my_city = "Munich, Germany";
   $MyCity = "Nymphenburg Palace, Munich - Germany";
   $myCity = "Munich, Germany, Europe";
   $_city = "Frankfurt";
   $_city_ = "Helsinki";
   $address = "Wellington Street, Toronto, Ontario(ON)";
   $address23 = "154 Wellington Street, Toronto, Ontario(ON)";
   $address23albert = "100 Main St., Lucky Lake, Saskatchewan(SK)";
   
   echo "<p>$x</p>";
   echo "<p>$y</p>";
   echo "<p>$city</p>";
   echo "<p>$mycity</p>";
   echo "<p>$my_city</p>";
   echo "<p>$MyCity</p>";
   echo "<p>$myCity</p>";
   echo "<p>$_city</p>";
   echo "<p>$_city_</p>";
   echo "<p>$address</p>";
   echo "<p>$address23</p>";
   echo "<p>$address23albert</p>";
?>

The output of this example, is:

Note - Variables in PHP must not contain space(s). Also, while naming a variable in PHP, you can not use a special character.

Note - The variable in PHP gets created at the time, when a value assigned to it.

Note - Since PHP is a loosely typed language, therefore the variable type depends on the value assigned to. For example:

<?php
   $x = 123;
   echo $x;
   $x = "codescracker.com";
   echo $x;
?>

The output of above PHP example, should be 123codescracker.com. In above example, see the same variable, that is $x, first holds the value 123 which is an integer type value, then again I've assigned a string to it.

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