Variable like a pot in PHP. We can hold many data using a variable. Like a text string "Hello World" or Integer value like 500. We can use a variable in the whole script if we set variable value top in the script. We don't need to use value repeatedly if we use variable. Here are some rules to declare a variable.
1. In PHP variable must start with "$" , otherwise it'll not work. 2. Variables are case sensitive . $the_variable & $The_Variable is not same. 3. You must start a variable with letter or "_" (under score). Any number isn't accepted starting in a variable. 4. PHP accepts alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ in variable. 5. PHP doesn't accept space in a variable. example- '$helloworld', '$HelloWorld', '$Hello_World' is correct variable but '$hello world' isn't a correct variable. Here is some example and discussion about PHP variable. Let's see how we write or declare a variable in script.
<?php $name = "Sajjad"; echo "Hello World!"; echo "<br/>"; echo "My name is "; echo $name; ?>
output, Hello World! My name is Sajjad Here is a simple math with variable,