如何在PHP中创建新的运算符？

=

<?
$test = array(\"3 is 5\", \"3 is not 5\"); 
$r = $teste [+( 3 != 5)];
echo $r; //return \"3 is not 5\" 
?>

<?php
    function defvar(&$var) {
        if (empty($var)) { $var = \'default value\'; }
    }

    // testing
    $set = \'test\';
    defvar($set);
    echo $set;

    defvar($notset);
    echo $notset;
?>

test
default value

<?php
    function setdefvar($var) {
        if (empty($var)) { return \'default value\'; }
        else { return $var; }
    }

    // testing
    $set = \'test\';
    $set = setdefvar($set);
    echo $set;

    $notset = setdefvar($notset);
    echo $notset;
?>

test
default value

/**
 * Global function to simplify the process of
 * checking to see if a value equates to true
 * and setting it to a new value if not.
 * 
 * @param mixed $var the original variable to
 * check and see if it equates to true/false
 * @param mixed $default the default value to
 * replace the variable if it equates to false
 * 
 * @return mixed returns the variable for
 * either further processing or assignment.
 */
function _d( &$var, $default ) {
    return $var = $var ?: $default;
}

_d( $variable, \'default value\' );
// $variable = $variable ?: \'default value\';

$variable1 = _d( $variable, \'default value\' ) . \'s\';
// $variable1 = ( $variable = $variable ?: \'default value\' ) . \'s\';

_d( $variable, _d( $variable1, \'default value\' ) );
// $variable = $variable ?: ( $variable1 = $variable1 ?: \'default value\' );

return $var = isset( $var ) ? $var : $default;}