Properties in PHP Classes: Defining Data Fields

• Class member variables are called properties. Sometimes they are referred as attributes or fields.
• The properties hold specific data and related with the class in which it has been defined.
• Declaring a property in a class is an easy task, use one of the keyword public, protected, or private followed by a normal variable declaration. If declared using var (compatibility with PHP 4), the property will be defined as public.
  
  • public : The property can be accessed from outside the class, either by the script or from another class
  • private : No access is granted from outside the class, either by the script or from another class.
  • protected : No access is granted from outside the class except a class that’s a child of the class with the protected property or method.

Example:

After an object is instantiated, you can access the property of a class using the object and -> operator. Any member declared with keyword "private" or "protected" cannot be accessed outside the method of the class.

Syntax

<span class="pln">

</span><span class="pun">&lt;?</span><span class="pln">php   
</span><span class="kwd">class</span><span class="pln"> </span><span class="typ">Myclass</span><span class="pln">
</span><span class="pun">{</span><span class="pln">
 </span><span class="kwd">public</span><span class="pln"> $font_size </span><span class="pun">=</span><span class="lit">10</span><span class="pun">;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
$f </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">MyClass</span><span class="pun">;</span><span class="pln">
echo $f</span><span class="pun">-&gt;</span><span class="pln">font_size</span><span class="pun">;</span><span class="pln">
</span><span class="pun">?&gt;</span><span class="pln">

</span>

Output

<span class="pln">
</span><span class="lit">10</span><span class="pln">
</span>

Note: There is a common mistake to use more than one dollar sign when accessing variables. In the above example there will be no $ sign before font_size (echo $f->font_size).

Another Example

Syntax

<span class="pln">

</span><span class="pun">&lt;?</span><span class="pln">php
</span><span class="kwd">class</span><span class="pln"> </span><span class="typ">Dress</span><span class="pun">{</span><span class="pln">  
	</span><span class="kwd">public</span><span class="pln"> $color </span><span class="pun">=</span><span class="pln"> </span><span class="str">"red"</span><span class="pun">;</span><span class="pln">  </span><span class="com">// The color of the dress </span><span class="pln">
	</span><span class="typ">Public</span><span class="pln"> $fabric </span><span class="pun">=</span><span class="pln"> </span><span class="str">"linen"</span><span class="pun">;</span><span class="pln"> </span><span class="com">// The fabric of the dress </span><span class="pln">
	</span><span class="typ">Public</span><span class="pln"> $design </span><span class="pun">=</span><span class="pln"> </span><span class="str">"Slim Fit Blazer"</span><span class="pun">;</span><span class="com">//The design of the dress   </span><span class="pln">

</span><span class="pun">}</span><span class="pln">

$dressObj </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Dress</span><span class="pun">();</span><span class="pln">
$dressObj</span><span class="pun">-&gt;</span><span class="pln">color </span><span class="pun">=</span><span class="pln"> </span><span class="str">"Black"</span><span class="pun">;</span><span class="pln">

var_dump</span><span class="pun">(</span><span class="pln">$dressObj</span><span class="pun">);</span><span class="pln"> 
echo </span><span class="str">"&lt;/br&gt;&lt;/br&gt;"</span><span class="pun">;</span><span class="pln">
print_r</span><span class="pun">(</span><span class="pln">$dressObj</span><span class="pun">);</span><span class="pln"> 
</span><span class="pun">?&gt;</span><span class="pln">

</span>