The difference between null, 0, and false in php updatedata false javascript:false async fals

The

empty() function is used to determine whether a string is empty.

As long as the variable is 0, null, '', false, empty() will be judged to be true.

    $num1='';
    $num2=0;
    echo $num1==$num2;
    echo '<br/>';
    echo $num1===$num2 ? '1' : '0';

The result is:

The reason is that variables in PHP are stored in C language structures. Empty strings, NULL, and false are all stored with a value of 0, and this structure There is a member variable like zend_uchartype;, which is used to save the type of the variable. The type of empty string is string, the type of NULL is NULL, and false is boolean. The === operator not only compares values, but also types.

Judge the empty string and 0 like this:

    $num1='';
    $num2=0;
    if(empty($num1) && $num1===''){
    	echo "true";
    }
    if(empty($num2) && $num2===0){
    	echo 'true';
    }

The result is:

The above introduces the differences between null, 0, and false in PHP, including the content of false and null. I hope it will be helpful to friends who are interested in PHP tutorials.