PHP – Variables

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A variable is simply a container that’s used to store both numeric and non-numeric information. And just as with any container, you can move it from  place to place, add stuff to it, or empty it out on the floor in a pile and fill it with something completely different.

PHP has some simple rules for naming variables. Every variable name must be preceded with dollar($) symbol and must begin with a letter or underscore character, optionally followed by more letters, numbers, or underscore character. Common punctuation characters, such as commas, quotation marks, or periods, are not permitted variable names; neither are spaces. So, for example, $root, $_num and $query are all valid variable names, while $58%, $1day, and email are all invalid variable names.

Assigning Values to Variables

Assigning value to a variables in PHP is quite easy: use the equality(=) symbol, which also happens to be PHP’s assignment operator. This assigns the value on the right side of the equation to the variable on the left.

To use a variable in a script, simply call it by name in an expression and PHP will replace it with its value when the script is executed. Here’s an example:

In this example, the variables $name is assigned the value ‘Simon’. The echo statement is then used to print the value of this variable to the Web page.

You can also assign a variable the value of another variable, or the result of calculation.

The following example demonstrates both these situations:

Destroying Variables

To destroy a variable, pass the variable to PHP’s aptly named unset() function, as in the following example:

Inspecting Variable Content

PHP offers the var_dump() function, which accepts a variable and X-ray it for you.

Here’s example:

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