php面试题 true、false、空串等的比较_php面试题 比较是否相等

true、false、空串等的比较

<?php
 
//  1.
 
    $str1 = null;
    $str2 = false;
    echo $str1==$str2 ? '相等' : '不相等';  //相等
 
    $str3 = '';
    $str4 = 0;
    echo $str3==$str4 ?'相等' : '不相等';   //相等
 
    $str5 = 0;
    $str6 = '0';
    echo $str5==$str6 ?'相等' : '不相等';   //相等
echo "<br>"."-------------------------------------------------"."<br>";
 
//  2.
 
    $a1 = null;
    $a2 = false;
    $a3 = 0;
    $a4 = '';
    $a5 = '0';
    $a6 = 'null';
    $a7 = array();
    $a8 = array(array());
    echo empty($a1) ? 'true' : 'false';        //true
    echo "<br>";
    echo empty($a2) ? 'true' : 'false';        //true
    echo "<br>";
    echo empty($a3) ? 'true' : 'false';        //true
    echo "<br>";
    echo empty($a4) ? 'true' : 'false';        //true
    echo "<br>";
    echo empty($a5) ? 'true' : 'false';        //true
    echo "<br>";
    echo empty($a6) ? 'true' : 'false';        //false
    echo "<br>";
    echo empty($a7) ? 'true' : 'false';        //true
    echo "<br>";
    echo empty($a8) ? 'true' : 'false';        //false
    echo "<br>";
 
echo "<br>"."-------------------------------------------------"."<br>";
 
//  3.
 
    $test = 'aaaaaa';
    $abc = & $test;
    unset($test);
    echo $abc;     //aaaaaa
 
 
echo "<br>"."-------------------------------------------------"."<br>";
 
//  4.
 
    $count=5;
    function get_count(){
        static $count = 0;
        return $count++;
    }
    echo $count." ";       //5
    ++$count;
    echo get_count()." ";   //0
    echo get_count()." ";   //1
 
 
echo "<br>"."-------------------------------------------------"."<br>";
 
//  5.
 
    $GLOBALS['var1'] = 5;
    $var2 = 1;
    function get_value(){
        global $var2;
        $var1 = 0;
        return $var2++;
    }
    get_value();
    echo $var1." ";        //5
    echo $var2." ";        //2
 
 
echo "<br>"."-------------------------------------------------"."<br>";
 
//  6.
 
 
    function get_arr($arr){
        unset($arr[0]);
    }
    $arr1 = array(1,2);
    $arr2 = array(1,2);
    get_arr($arr1);
    get_arr($arr2);
 
    echo count($arr1)." "; //2
    echo count($arr2);     //2
 
echo "<br>"."--------------------------------------------------"."<br>";
 
//  7.
 
    $a = 3;
    $b = 5;
    if($a = 5 || $b = 7){
        $a++;
        $b++;
    }
    echo $a." ".$b;        //分別是1和6
 
?>