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PHPVariables_075026.ppt
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- 2. What is a variable? A variable in PHP is the name of the memory location that holds data. In PHP, a variable is declared using the $ sign followed by the variable name. The main way to store information in the middle of a PHP program is by using a variable. 2
- 3. PHPVariable Rules • A variablemust start with a dollar ($) sign, followed by the variable name. • It can only contain alpha-numeric character and underscore (A-z, 0-9, _). • A variable name must start with a letter or underscore (_) character. • A PHP variable name cannot contain spaces. • One thing to be kept in mind that the variable name cannot start with a number or special symbols. • PHP variables are case-sensitive, so $name and $NAME both are treated as different variable. 3
- 4. Types of Variable Datatypes utilized by PHP to declare or build variables: • Null • Doubles • Integers • Strings • Booleans • Resources • Objects • Arrays 4
- 5. Assignment A variableis said to be assigned a value in an assignment statement. E.g. $NumberHours = 45; $WorkerFirstName = “Pete”; The assignment statement should not be thought of as expressing mathematical equality rather it a set of instructions to evaluate the expression on the right hand side and give the variable on the left hand side the value that results. Thus $Counter = $Counter + 1; Makes sense as an assignment statement even though it makes no sense as mathematics. 5
- 6. PHP Variables Scopes PHPVariables Scope In PHP, variables can be declared anywhere in the script.The scope of a variable is the part of the script where the variable can be referenced/used. PHP has three different variable scopes: • Local • Global • Static 6
- 7. Local Variable The variablesthat are declared within a function are called local variables for that function. These local variables have their scope only in that particular function in which they are declared. This means that these variables cannot be accessed outside the function, as they have local scope. Example: <?php function local_var() { $num = 45; //local variable echo "Local variable declared inside the function is: ". $ num; } local_var(); ?> 7
- 8. Global Variable The globalvariables are the variables that are declared outside the function. These variables can be accessed anywhere in the program. To access the global variable within a function, use the GLOBAL keyword before the variable. However, these variables can be directly accessed or used outside the function without any keyword. Therefore there is no need to use any keyword to access a global variable outside the function. Ex:<?php $name = “VK"; //global variable function global_var() { echo "Variable inside the function: ". $name; echo "</br>"; } global_var(); ?> 8
- 9. Static Variable A staticvariable is the attribute of PHP to erase the variable once it finishes its execution and the memory is liberated. However, in some cases, we really want to store the variables even after the fulfillment of function execution. Ex: <?php function keep_track() { STATIC $count = 0; $count++; print $count; print "<br/>"; } keep_track(); keep_track(); keep_track(); ?> 9
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