PHP Variables

Description

A variable is a container holding a certain value.

Syntax

Variables in PHP beginning with $ followed by a letter or an underscore, then any combination of letters, numbers, and the underscore character.

Here are the rules we would follow to name variables.

• Variable names begin with a dollar sign ( $ )
• The first character after the dollar sign must be a letter or an underscore
• The remaining characters in the name may be letters, numbers, or underscores without a fixed limit

Example

We cannot start a variable with a number. A list of valid and invalid variable names is shown in the following table.

Variables are case-sensitive. $Foo is not the same variable as $foo.

Variable substitution

In PHP we can write variable name into a long string and PHP knows how to replace the variable with its value. Here is a script showing assigning and outputting data.

<?php/*ww  w  .  j a va2  s .co  m*/
       $name = "java2s.com";
       print "Your name is $name\n";
       $name2 = $name;
       print 'Goodbye, $name2!\n';
?>

The code above generates the following result.

PHP will not perform variable substitution inside single-quoted strings, and won't replace most escape characters.

In the following example, we can see that:

• In double-quoted strings, PHP will replace $name with its value;
• In a single-quoted string, PHP will output the text $name just like that.

<?php//w  w  w. ja  v a 2s . c o m
        $food = "grapefruit";
        print "These ${food}s aren't ripe yet.";
        print "These {$food}s aren't ripe yet.";
?>

The code above generates the following result.

The braces {} tells where the variable ends.