How does PHP determine whether a variable is empty and has a value? (Picture + video tutorial)

During the development of a PHP project or when a novice is learning PHP, you may encounter prompts such as a certain variable does not exist or a certain variable is empty. At this point we need to know how PHP determines whether a variable is empty or whether it exists. This question is also one of the common PHP interview questions.

This article will give you a detailed introduction to the specific methods of PHP to determine whether a variable is empty and PHP to determine whether a variable exists.

Below we will introduce it to you in detail through a simple code example.

1. The isset function determines whether the variable exists.

<?php
$a = &#39;&#39;;
var_dump(isset($a));

Here we use the isset function to determine whether the $a variable exists. The judgment results are as follows Picture:

#If true is shown in the picture, it means that the variable $a exists.

<?php
$a = &#39;&#39;;
var_dump(isset($x));

Determine whether the $x variable exists. The judgment result is as follows:

If false is shown in the figure, it means that the variable $x does not exist. .

Summary 1: The isset function in PHP is used to detect whether the variable exists, is set and is not NULL. Returns TRUE if a variable exists and its value is not NULL, FALSE otherwise.

2. The empty function determines whether the variable is empty.

<?php
$a = &#39;&#39;;
var_dump(empty($a));

Here we use the empty function to determine whether the value of the variable $a is empty. The result is as shown below:

We will enter a space into the variable $a:

<?php
$a = &#39; &#39;;//此处有空格
var_dump(empty($a));

The result printed at this time is as follows:

Summary 2: The empty function in PHP is used to check whether a variable is empty. Returns FALSE when a variable exists and is a non-null, non-zero value Otherwise, return TRUE.

The above is an introduction to the specific methods of PHP to determine whether a variable is empty and determine whether a variable exists. Hope it helps those in need!

If you want to know more about PHP, you can follow the PHP video tutorial on the PHP Chinese website. Everyone is welcome to refer to and learn!

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