Incrementing/Decrementing Operators

PHP supports C-style pre- and post-increment and decrement operators.

表格 11-5. Increment/decrement Operators

Example Name Effect
++$a Pre-increment Increments $a by one, then returns $a.
$a++ Post-increment Returns $a, then increments $a by one.
--$a Pre-decrement Decrements $a by one, then returns $a.
$a-- Post-decrement Returns $a, then decrements $a by one.

Here's a simple example script:

 ?php
echo " h3 Postincrement /h3 ";
$a = 5;
echo "Should be 5: " . $a++ . " br / \n";
echo "Should be 6: " . $a . " br / \n";

echo " h3 Preincrement /h3 ";
$a = 5;
echo "Should be 6: " . ++$a . " br / \n";
echo "Should be 6: " . $a . " br / \n";

echo " h3 Postdecrement /h3 ";
$a = 5;
echo "Should be 5: " . $a-- . " br / \n";
echo "Should be 4: " . $a . " br / \n";

echo " h3 Predecrement /h3 ";
$a = 5;
echo "Should be 4: " . --$a . " br / \n";
echo "Should be 4: " . $a . " br / \n";
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