# Variables in PHP

## Variables in PHP

<?php
$var = 'Bob';$Var = 'Joe';
echo "$var,$Var";      // outputs "Bob, Joe"

$4site = 'not yet'; // invalid; starts with a number$_4site = 'not yet';    // valid; starts with an underscore
$täyte = 'mansikka'; // valid; 'ä' is (Extended) ASCII 228. ?> • Variables in PHP are represented by a dollar sign followed by the name of the variable. • The variable name is case-sensitive. • Variable names follow the same rules as other labels in PHP. • A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. • By default, variables are always assigned by value. • PHP also offers another way to assign values to variables: assign by reference. • It is not necessary to initialize variables in PHP however it is a very good practice. • Uninitialized variables have a default value of their type depending on the context in which they are used - booleans default to FALSE, integers and floats default to zero, strings (e.g. used in echo) are set as an empty string and arrays become to an empty array. • Relying on the default value of an uninitialized variable is problematic in the case of including one file into another which uses the same variable name. ### Assign by reference <?php$foo = 'Bob';              // Assign the value 'Bob' to $foo$bar = &$foo; // Reference$foo via $bar.$bar = "My name is $bar"; // Alter$bar...
echo $bar; echo$foo;                 // \$foo is altered too.
?>
• This means that the new variable simply references (in other words, "becomes an alias for" or "points to") the original variable.
• Changes to the new variable affect the original, and vice versa.
• To assign by reference, simply prepend an ampersand (&) to the beginning of the variable which is being assigned (the source variable).
• Only named variables may be assigned by reference.

Variables in PHP

## Variables in PHP — Structure map

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