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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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