php引用,对象对比例子

<?php
function bool2str($bool)
{
    if ($bool === false) {
        return 'FALSE';
    } else {
        return 'TRUE';
    }
}
 
function compareObjects(&$o1, &$o2)
{
    echo 'o1 == o2 : ' . bool2str($o1 == $o2) . "\n";
    echo 'o1 != o2 : ' . bool2str($o1 != $o2) . "\n";
    echo 'o1 === o2 : ' . bool2str($o1 === $o2) . "\n";
    echo 'o1 !== o2 : ' . bool2str($o1 !== $o2) . "\n";
}
 
class Flag
{
    public $flag;
 
    function Flag($flag = true) {
        $this->flag = $flag;
    }
}
 
class OtherFlag
{
    public $flag;
 
    function OtherFlag($flag = true) {
        $this->flag = $flag;
    }
}
 
$o = new Flag();
$p = new Flag();
$q = $o;
$s = &$o;
$r = new OtherFlag();
 
echo "Two instances of the same class\n";
compareObjects($o, $p);
 
echo "\nTwo references to the same instance\n";
compareObjects($o, $q);
 
echo "\nTwo references to the same instance\n";
compareObjects($s, $q);
 
echo "\nInstances of two different classes\n";
compareObjects($o, $r);
?>

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