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> PHP supports C-style pre- and post-increment and decrement
operators.
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>Tabel 10-5. Increment/decrement Operators</B
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>Example</TH
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>Name</TH
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>Effect</TH
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><TD
>++$a</TD
><TD
>Pre-increment</TD
><TD
>Increments $a by one, then returns $a.</TD
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><TD
>$a++</TD
><TD
>Post-increment</TD
><TD
>Returns $a, then increments $a by one.</TD
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><TD
>--$a</TD
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>Pre-decrement</TD
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>Decrements $a by one, then returns $a.</TD
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>$a--</TD
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>Post-decrement</TD
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>Returns $a, then decrements $a by one.</TD
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> Here's a simple example script:
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><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">echo </font><font color="#DD0000">"<h3>Postincrement</h3>"</font><font color="#007700">;<br /></font><font color="#0000BB">$a </font><font color="#007700">= </font><font color="#0000BB">5</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 5: " </font><font color="#007700">. </font><font color="#0000BB">$a</font><font color="#007700">++ . </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 6: " </font><font color="#007700">. </font><font color="#0000BB">$a </font><font color="#007700">. </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br /><br />echo </font><font color="#DD0000">"<h3>Preincrement</h3>"</font><font color="#007700">;<br /></font><font color="#0000BB">$a </font><font color="#007700">= </font><font color="#0000BB">5</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 6: " </font><font color="#007700">. ++</font><font color="#0000BB">$a </font><font color="#007700">. </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 6: " </font><font color="#007700">. </font><font color="#0000BB">$a </font><font color="#007700">. </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br /><br />echo </font><font color="#DD0000">"<h3>Postdecrement</h3>"</font><font color="#007700">;<br /></font><font color="#0000BB">$a </font><font color="#007700">= </font><font color="#0000BB">5</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 5: " </font><font color="#007700">. </font><font color="#0000BB">$a</font><font color="#007700">-- . </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 4: " </font><font color="#007700">. </font><font color="#0000BB">$a </font><font color="#007700">. </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br /><br />echo </font><font color="#DD0000">"<h3>Predecrement</h3>"</font><font color="#007700">;<br /></font><font color="#0000BB">$a </font><font color="#007700">= </font><font color="#0000BB">5</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 4: " </font><font color="#007700">. --</font><font color="#0000BB">$a </font><font color="#007700">. </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br />echo </font><font color="#DD0000">"Should be 4: " </font><font color="#007700">. </font><font color="#0000BB">$a </font><font color="#007700">. </font><font color="#DD0000">"<br />\n"</font><font color="#007700">;<br /></font><font color="#0000BB">?></font>
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>
</P
><P
> PHP follows Perl's convention when dealing with arithmetic operations
on character variables and not C's. For example, in Perl 'Z'+1 turns
into 'AA', while in C 'Z'+1 turns into '[' ( ord('Z') == 90, ord('[') == 91 ).
Note that character variables can be incremented but not decremented.
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>Exemplu 10-1. Arithmetic Operations on Character Variables</B
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><code><font color="#000000">
<font color="#0000BB"><?php<br />$i </font><font color="#007700">= </font><font color="#DD0000">'W'</font><font color="#007700">;<br />for(</font><font color="#0000BB">$n</font><font color="#007700">=</font><font color="#0000BB">0</font><font color="#007700">; </font><font color="#0000BB">$n</font><font color="#007700"><</font><font color="#0000BB">6</font><font color="#007700">; </font><font color="#0000BB">$n</font><font color="#007700">++)<br /> echo ++</font><font color="#0000BB">$i </font><font color="#007700">. </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /><br /></font><font color="#FF8000">/*<br /> Produces the output similar to the following:<br /><br />X<br />Y<br />Z<br />AA<br />AB<br />AC<br /><br />*/<br /></font><font color="#0000BB">?></font>
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