| 1 | <HTML
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| 2 | ><HEAD
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| 3 | ><TITLE
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| 4 | >::</TITLE
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| 5 | ><META
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| 6 | NAME="GENERATOR"
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| 7 | CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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| 8 | REL="HOME"
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| 9 | TITLE="Manuál PHP"
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| 10 | HREF="index.html"><LINK
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| 11 | REL="UP"
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| 12 | TITLE="Classes and Objects"
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| 13 | HREF="language.oop.html"><LINK
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| 14 | REL="PREVIOUS"
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| 15 | TITLE="Constructors"
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| 16 | HREF="language.oop.constructor.html"><LINK
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| 17 | REL="NEXT"
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| 18 | TITLE="parent"
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| 19 | HREF="keyword.parent.html"><META
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| 20 | HTTP-EQUIV="Content-type"
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| 21 | CONTENT="text/html; charset=ISO-8859-2"></HEAD
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| 22 | ><BODY
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| 23 | CLASS="sect1"
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| 24 | BGCOLOR="#FFFFFF"
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| 25 | TEXT="#000000"
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| 26 | LINK="#0000FF"
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| 27 | VLINK="#840084"
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| 28 | ALINK="#0000FF"
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| 29 | ><DIV
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| 30 | CLASS="NAVHEADER"
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| 31 | ><TABLE
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| 32 | SUMMARY="Header navigation table"
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| 33 | WIDTH="100%"
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| 34 | BORDER="0"
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| 35 | CELLPADDING="0"
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| 36 | CELLSPACING="0"
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| 37 | ><TR
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| 38 | ><TH
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| 39 | COLSPAN="3"
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| 40 | ALIGN="center"
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| 41 | >Manuál PHP</TH
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| 42 | ></TR
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| 43 | ><TR
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| 44 | ><TD
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| 45 | WIDTH="10%"
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| 46 | ALIGN="left"
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| 47 | VALIGN="bottom"
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| 48 | ><A
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| 49 | HREF="language.oop.constructor.html"
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| 50 | ACCESSKEY="P"
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| 51 | >Pøedcházející</A
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| 52 | ></TD
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| 53 | ><TD
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| 54 | WIDTH="80%"
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| 55 | ALIGN="center"
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| 56 | VALIGN="bottom"
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| 57 | >Kapitola 14. Classes and Objects</TD
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| 58 | ><TD
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| 59 | WIDTH="10%"
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| 60 | ALIGN="right"
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| 61 | VALIGN="bottom"
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| 62 | ><A
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| 63 | HREF="keyword.parent.html"
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| 64 | ACCESSKEY="N"
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| 65 | >Dal¹í</A
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| 66 | ></TD
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| 67 | ></TR
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| 68 | ></TABLE
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| 69 | ><HR
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| 70 | ALIGN="LEFT"
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| 71 | WIDTH="100%"></DIV
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| 72 | ><DIV
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| 73 | CLASS="sect1"
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| 74 | ><H1
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| 75 | CLASS="sect1"
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| 76 | ><A
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| 77 | NAME="keyword.paamayim-nekudotayim"
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| 78 | ></A
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| 79 | ><TT
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| 80 | CLASS="literal"
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| 81 | >::</TT
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| 82 | ></H1
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| 83 | ><DIV
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| 84 | CLASS="caution"
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| 85 | ><P
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| 86 | ></P
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| 87 | ><TABLE
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| 88 | CLASS="caution"
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| 89 | BORDER="1"
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| 90 | WIDTH="100%"
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| 91 | ><TR
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| 92 | ><TD
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| 93 | ALIGN="CENTER"
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| 94 | ><B
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| 95 | >Výstraha</B
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| 96 | ></TD
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| 97 | ></TR
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| 98 | ><TR
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| 99 | ><TD
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| 100 | ALIGN="LEFT"
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| 101 | ><P
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| 102 | > The following is valid for PHP 4 only.
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| 103 | </P
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| 104 | ></TD
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| 105 | ></TR
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| 106 | ></TABLE
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| 107 | ></DIV
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| 108 | ><P
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| 109 | > Sometimes it is useful to refer to functions and variables
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| 110 | in base classes or to refer to functions in classes that
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| 111 | have not yet any instances. The :: operator is being used
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| 112 | for this.
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| 113 | </P
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| 114 | ><DIV
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| 115 | CLASS="informalexample"
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| 116 | ><A
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| 117 | NAME="AEN5737"
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| 118 | ></A
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| 119 | ><P
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| 120 | ></P
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| 121 | ><TABLE
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| 122 | BORDER="0"
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| 123 | BGCOLOR="#E0E0E0"
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| 124 | CELLPADDING="5"
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| 125 | ><TR
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| 126 | ><TD
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| 127 | ><PRE
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| 128 | CLASS="php"
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| 129 | >class A
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| 130 | {
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| 131 | function example()
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| 132 | {
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| 133 | echo "I am the original function A::example().<br>\n";
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| 134 | }
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| 135 | }
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| 136 |
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| 137 | class B extends A
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| 138 | {
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| 139 | function example()
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| 140 | {
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| 141 | echo "I am the redefined function B::example().<br>\n";
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| 142 | A::example();
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| 143 | }
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| 144 | }
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| 145 |
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| 146 | // there is no object of class A.
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| 147 | // this will print
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| 148 | // I am the original function A::example().<br>
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| 149 | A::example();
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| 150 |
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| 151 | // create an object of class B.
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| 152 | $b = new B;
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| 153 |
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| 154 | // this will print
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| 155 | // I am the redefined function B::example().<br>
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| 156 | // I am the original function A::example().<br>
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| 157 | $b->example();</PRE
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| 158 | ></TD
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| 159 | ></TR
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| 160 | ></TABLE
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| 161 | ><P
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| 162 | ></P
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| 163 | ></DIV
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| 164 | ><P
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| 165 | > The above example calls the function example() in
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| 166 | class A, but there is no object of class A, so that
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| 167 | we cannot write $a->example() or similar. Instead we
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| 168 | call example() as a 'class function', that is, as a
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| 169 | function of the class itself, not any object of that
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| 170 | class.
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| 171 | </P
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| 172 | ><P
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| 173 | > There are class functions, but there are no class variables.
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| 174 | In fact, there is no object at all at the time of the call.
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| 175 | Thus, a class function may not use any object variables (but
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| 176 | it can use local and global variables), and it may no use
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| 177 | $this at all.
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| 178 | </P
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| 179 | ><P
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| 180 | > In the above example, class B redefines the function example().
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| 181 | The original definition in class A is shadowed
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| 182 | and no longer available, unless you are refering specifically
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| 183 | to the implementation of example() in class A using the
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| 184 | ::-operator. Write A::example() to do this (in fact, you
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| 185 | should be writing parent::example(), as shown in the next
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| 186 | section).
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| 187 | </P
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| 188 | ><P
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| 189 | > In this context, there is a current object and it may
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| 190 | have object variables. Thus, when used from WITHIN an
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| 191 | object function, you may use $this and object variables.
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| 192 | </P
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| 193 | ></DIV
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| 194 | ><DIV
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| 195 | CLASS="NAVFOOTER"
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| 196 | ><HR
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| 197 | ALIGN="LEFT"
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| 198 | WIDTH="100%"><TABLE
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| 199 | SUMMARY="Footer navigation table"
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| 200 | WIDTH="100%"
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| 201 | BORDER="0"
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| 202 | CELLPADDING="0"
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| 203 | CELLSPACING="0"
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| 204 | ><TR
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| 205 | ><TD
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| 206 | WIDTH="33%"
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| 207 | ALIGN="left"
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| 208 | VALIGN="top"
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| 209 | ><A
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| 210 | HREF="language.oop.constructor.html"
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| 211 | ACCESSKEY="P"
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| 212 | >Pøedcházející</A
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| 213 | ></TD
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| 214 | ><TD
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| 215 | WIDTH="34%"
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| 216 | ALIGN="center"
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| 217 | VALIGN="top"
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| 218 | ><A
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| 219 | HREF="index.html"
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| 220 | ACCESSKEY="H"
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| 221 | >Domù</A
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| 222 | ></TD
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| 223 | ><TD
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| 224 | WIDTH="33%"
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| 225 | ALIGN="right"
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| 226 | VALIGN="top"
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| 227 | ><A
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| 228 | HREF="keyword.parent.html"
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| 229 | ACCESSKEY="N"
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| 230 | >Dal¹í</A
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| 231 | ></TD
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| 232 | ></TR
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| 233 | ><TR
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| 234 | ><TD
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| 235 | WIDTH="33%"
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| 236 | ALIGN="left"
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| 237 | VALIGN="top"
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| 238 | ><TT
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| 239 | CLASS="literal"
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| 240 | >Constructors</TT
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| 241 | ></TD
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| 242 | ><TD
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| 243 | WIDTH="34%"
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| 244 | ALIGN="center"
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| 245 | VALIGN="top"
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| 246 | ><A
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| 247 | HREF="language.oop.html"
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| 248 | ACCESSKEY="U"
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| 249 | >Nahoru</A
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| 250 | ></TD
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| 251 | ><TD
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| 252 | WIDTH="33%"
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| 253 | ALIGN="right"
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| 254 | VALIGN="top"
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| 255 | ><TT
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| 256 | CLASS="literal"
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| 257 | >parent</TT
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| 258 | ></TD
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| 259 | ></TR
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| 260 | ></TABLE
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| 261 | ></DIV
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| 262 | ></BODY
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| 263 | ></HTML
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| 264 | >
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